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Transmembrane protein

February 16, 2024

A transmembrane protein is a type of integral membrane protein that spans the entirety of the cell membrane. Many transmembrane proteins function as gateways to permit the transport of specific substances across the membrane. They frequently undergo significant conformational changes to move a substance through the membrane. They are usually highly hydrophobic and aggregate and precipitate in water. They require detergents or nonpolar solvents for extraction, although some of them (beta-barrels) can be also extracted using denaturing agents.

Schematic representation of transmembrane proteins: 1) a single-pass membrane protein (α-helix) 2) a multipass membrane protein (α-helix) 3) a multipass membrane protein β-sheet. The membrane is represented in light yellow.

The peptide sequence that spans the membrane, or the transmembrane segment, is largely hydrophobic and can be visualized using the hydropathy plot.[1] Depending on the number of transmembrane segments, transmembrane proteins can be classified as single-pass membrane proteins, or as multipass membrane proteins.[2] Some other integral membrane proteins are called monotopic, meaning that they are also permanently attached to the membrane, but do not pass through it.[3]

Types edit

Classification by structure edit

There are two basic types of transmembrane proteins:[4] alpha-helical and beta barrels. Alpha-helical proteins are present in the inner membranes of bacterial cells or the plasma membrane of eukaryotic cells, and sometimes in the bacterial outer membrane.[5] This is the major category of transmembrane proteins. In humans, 27% of all proteins have been estimated to be alpha-helical membrane proteins.[6] Beta-barrel proteins are so far found only in outer membranes of gram-negative bacteria, cell walls of gram-positive bacteria, outer membranes of mitochondria and chloroplasts, or can be secreted as pore-forming toxins. All beta-barrel transmembrane proteins have simplest up-and-down topology, which may reflect their common evolutionary origin and similar folding mechanism.[citation needed]

In addition to the protein domains, there are unusual transmembrane elements formed by peptides. A typical example is gramicidin A, a peptide that forms a dimeric transmembrane β-helix.[7] This peptide is secreted by gram-positive bacteria as an antibiotic. A transmembrane polyproline-II helix has not been reported in natural proteins. Nonetheless, this structure was experimentally observed in specifically designed artificial peptides.[8]

Classification by topology edit

This classification refers to the position of the protein N- and C-termini on the different sides of the lipid bilayer. Types I, II, III and IV are single-pass molecules. Type I transmembrane proteins are anchored to the lipid membrane with a stop-transfer anchor sequence and have their N-terminal domains targeted to the endoplasmic reticulum (ER) lumen during synthesis (and the extracellular space, if mature forms are located on cell membranes). Type II and III are anchored with a signal-anchor sequence, with type II being targeted to the ER lumen with its C-terminal domain, while type III have their N-terminal domains targeted to the ER lumen. Type IV is subdivided into IV-A, with their N-terminal domains targeted to the cytosol and IV-B, with an N-terminal domain targeted to the lumen.[9] The implications for the division in the four types are especially manifest at the time of translocation and ER-bound translation, when the protein has to be passed through the ER membrane in a direction dependent on the type.[citation needed]

 
Group I and II transmembrane proteins have opposite final topologies. Group I proteins have the N terminus on the far side and C terminus on the cytosolic side. Group II proteins have the C terminus on the far side and N terminus in the cytosol. However final topology not the only criterion for defining transmembrane protein groups, rather location of topogenic determinants and mechanism of assembly is considered in the classification[10]

3D structure edit

 
Increase in the number of 3D structures of membrane proteins known

Membrane protein structures can be determined by X-ray crystallography, electron microscopy or NMR spectroscopy.[11] The most common tertiary structures of these proteins are transmembrane helix bundle and beta barrel. The portion of the membrane proteins that are attached to the lipid bilayer (see annular lipid shell) consist mostly of hydrophobic amino acids.[12]

Membrane proteins which have hydrophobic surfaces, are relatively flexible and are expressed at relatively low levels. This creates difficulties in obtaining enough protein and then growing crystals. Hence, despite the significant functional importance of membrane proteins, determining atomic resolution structures for these proteins is more difficult than globular proteins.[13] As of January 2013 less than 0.1% of protein structures determined were membrane proteins despite being 20–30% of the total proteome.[14] Due to this difficulty and the importance of this class of proteins methods of protein structure prediction based on hydropathy plots, the positive inside rule and other methods have been developed.[15][16][17]

Thermodynamic stability and folding edit

Stability of alpha-helical transmembrane proteins edit

Transmembrane alpha-helical (α-helical) proteins are unusually stable judging from thermal denaturation studies, because they do not unfold completely within the membranes (the complete unfolding would require breaking down too many α-helical H-bonds in the nonpolar media). On the other hand, these proteins easily misfold, due to non-native aggregation in membranes, transition to the molten globule states, formation of non-native disulfide bonds, or unfolding of peripheral regions and nonregular loops that are locally less stable.[citation needed]

It is also important to properly define the unfolded state. The unfolded state of membrane proteins in detergent micelles is different from that in the thermal denaturation experiments.[citation needed] This state represents a combination of folded hydrophobic α-helices and partially unfolded segments covered by the detergent. For example, the "unfolded" bacteriorhodopsin in SDS micelles has four transmembrane α-helices folded, while the rest of the protein is situated at the micelle-water interface and can adopt different types of non-native amphiphilic structures. Free energy differences between such detergent-denatured and native states are similar to stabilities of water-soluble proteins (< 10 kcal/mol).[citation needed]

Folding of α-helical transmembrane proteins edit

Refolding of α-helical transmembrane proteins in vitro is technically difficult. There are relatively few examples of the successful refolding experiments, as for bacteriorhodopsin. In vivo, all such proteins are normally folded co-translationally within the large transmembrane translocon. The translocon channel provides a highly heterogeneous environment for the nascent transmembrane α-helices. A relatively polar amphiphilic α-helix can adopt a transmembrane orientation in the translocon (although it would be at the membrane surface or unfolded in vitro), because its polar residues can face the central water-filled channel of the translocon. Such mechanism is necessary for incorporation of polar α-helices into structures of transmembrane proteins. The amphiphilic helices remain attached to the translocon until the protein is completely synthesized and folded. If the protein remains unfolded and attached to the translocon for too long, it is degraded by specific "quality control" cellular systems.[citation needed]

Stability and folding of beta-barrel transmembrane proteins edit

Stability of beta barrel (β-barrel) transmembrane proteins is similar to stability of water-soluble proteins, based on chemical denaturation studies. Some of them are very stable even in chaotropic agents and high temperature. Their folding in vivo is facilitated by water-soluble chaperones, such as protein Skp. It is thought that β-barrel membrane proteins come from one ancestor even having different number of sheets which could be added or doubled during evolution. Some studies show a huge sequence conservation among different organisms and also conserved amino acids which hold the structure and help with folding.[18]

3D structures edit

See also: Transporter Classification Database

Light absorption-driven transporters edit

Oxidoreduction-driven transporters edit

Electrochemical potential-driven transporters edit

  • Proton or sodium translocating F-type and V-type ATPases

P-P-bond hydrolysis-driven transporters edit

Porters (uniporters, symporters, antiporters) edit

Alpha-helical channels including ion channels edit

Enzymes edit

Proteins with alpha-helical transmembrane anchors edit

Beta-barrels composed of a single polypeptide chain edit

Note: n and S are, respectively, the number of beta-strands and the "shear number"[20] of the beta-barrel

Beta-barrels composed of several polypeptide chains edit

See also edit

References edit

  1. ^ Manor, Joshua; Feldblum, Esther S.; Arkin, Isaiah T. (2012). "Environment Polarity in Proteins Mapped Noninvasively by FTIR Spectroscopy". The Journal of Physical Chemistry Letters. 3 (7): 939–944. doi:10.1021/jz300150v. PMC 3341589. PMID 22563521.
  2. ^ Alberts, Bruce; Johnson, Alexander; Lewis, Julian; Raff, Martin; Roberts, Keith; Walter, Peter (2002). "Membrane Proteins". Molecular Biology of the Cell. 4th edition. Garland Science. Retrieved 31 October 2023.
  3. ^ Steven R. Goodman (2008). Medical cell biology. Academic Press. pp. 37–. ISBN 978-0-12-370458-0. Retrieved 24 November 2010.
  4. ^ Jin Xiong (2006). Essential bioinformatics. Cambridge University Press. pp. 208–. ISBN 978-0-521-84098-9. Retrieved 13 November 2010.
  5. ^ alpha-helical proteins in outer membranes include Stannin and certain lipoproteins, and others
  6. ^ Almén MS, Nordström KJ, Fredriksson R, Schiöth HB (2009). "Mapping the human membrane proteome: a majority of the human membrane proteins can be classified according to function and evolutionary origin". BMC Biol. 7: 50. doi:10.1186/1741-7007-7-50. PMC 2739160. PMID 19678920.
  7. ^ Nicholson, L. K.; Cross, T. A. (1989). "Gramicidin cation channel: an experimental determination of the right-handed helix sense and verification of .beta.-type hydrogen bonding". Biochemistry. 28 (24): 9379–9385. doi:10.1021/bi00450a019. PMID 2482072.
  8. ^ Kubyshkin, Vladimir; Grage, Stephan L.; Ulrich, Anne S.; Budisa, Nediljko (2019). "Bilayer thickness determines the alignment of model polyproline helices in lipid membranes". Physical Chemistry Chemical Physics. 21 (40): 22396–22408. Bibcode:2019PCCP...2122396K. doi:10.1039/c9cp02996f. PMID 31577299.
  9. ^ Harvey Lodish etc.; Molecular Cell Biology, Sixth edition, p.546
  10. ^ Goder, Veit; Spiess, Martin (31 August 2001). "Topogenesis of membrane proteins: determinants and dynamics". FEBS Letters. 504 (3): 87–93. doi:10.1016/S0014-5793(01)02712-0. PMID 11532438.
  11. ^ Cross, Timothy A.; Sharma, Mukesh; Yi, Myunggi; Zhou, Huan-Xiang (2011). "Influence of Solubilizing Environments on Membrane Protein Structures". Trends in Biochemical Sciences. 36 (2): 117–125. doi:10.1016/j.tibs.2010.07.005. PMC 3161620. PMID 20724162.
  12. ^ White, Stephen. "General Principle of Membrane Protein Folding and Stability". Stephen White Laboratory Homepage. 10 Nov. 2009. web.[verification needed]
  13. ^ Carpenter, Elisabeth P; Beis, Konstantinos; Cameron, Alexander D; Iwata, So (October 2008). "Overcoming the challenges of membrane protein crystallography". Current Opinion in Structural Biology. 18 (5): 581–586. doi:10.1016/j.sbi.2008.07.001. PMC 2580798. PMID 18674618.
  14. ^ . Archived from the original on 2013-12-25. Retrieved 2016-05-01.
  15. ^ Elofsson, Arne; Heijne, Gunnar von (7 June 2007). "Membrane Protein Structure: Prediction versus Reality". Annual Review of Biochemistry. 76 (1): 125–140. CiteSeerX 10.1.1.332.4023. doi:10.1146/annurev.biochem.76.052705.163539. PMID 17579561.
  16. ^ Chen, Chien Peter; Rost, Burkhard (2002). "State-of-the-art in membrane protein prediction". Applied Bioinformatics. 1 (1): 21–35. CiteSeerX 10.1.1.134.7424. PMID 15130854.
  17. ^ Hopf, Thomas A.; Colwell, Lucy J.; Sheridan, Robert; Rost, Burkhard; Sander, Chris; Marks, Debora S. (June 2012). "Three-Dimensional Structures of Membrane Proteins from Genomic Sequencing". Cell. 149 (7): 1607–1621. doi:10.1016/j.cell.2012.04.012. PMC 3641781. PMID 22579045.
  18. ^ Michalik, Marcin; Orwick-Rydmark, Marcella; Habeck, Michael; Alva, Vikram; Arnold, Thomas; Linke, Dirk; Permyakov, Eugene A. (3 August 2017). "An evolutionarily conserved glycine-tyrosine motif forms a folding core in outer membrane proteins". PLOS ONE. 12 (8): e0182016. Bibcode:2017PLoSO..1282016M. doi:10.1371/journal.pone.0182016. PMC 5542473. PMID 28771529.
  19. ^ Bracey MH, Hanson MA, Masuda KR, Stevens RC, Cravatt BF (November 2002). "Structural adaptations in a membrane enzyme that terminates endocannabinoid signaling". Science. 298 (5599): 1793–6. Bibcode:2002Sci...298.1793B. doi:10.1126/science.1076535. PMID 12459591. S2CID 22656813.
  20. ^ Murzin AG, Lesk AM, Chothia C (March 1994). "Principles determining the structure of beta-sheet barrels in proteins. I. A theoretical analysis". J. Mol. Biol. 236 (5): 1369–81. doi:10.1016/0022-2836(94)90064-7. PMID 8126726.

February 16, 2024
transmembrane, protein, transmembrane, protein, type, integral, membrane, protein, that, spans, entirety, cell, membrane, many, transmembrane, proteins, function, gateways, permit, transport, specific, substances, across, membrane, they, frequently, undergo, s. A transmembrane protein is a type of integral membrane protein that spans the entirety of the cell membrane Many transmembrane proteins function as gateways to permit the transport of specific substances across the membrane They frequently undergo significant conformational changes to move a substance through the membrane They are usually highly hydrophobic and aggregate and precipitate in water They require detergents or nonpolar solvents for extraction although some of them beta barrels can be also extracted using denaturing agents Schematic representation of transmembrane proteins 1 a single pass membrane protein a helix 2 a multipass membrane protein a helix 3 a multipass membrane protein b sheet The membrane is represented in light yellow The peptide sequence that spans the membrane or the transmembrane segment is largely hydrophobic and can be visualized using the hydropathy plot 1 Depending on the number of transmembrane segments transmembrane proteins can be classified as single pass membrane proteins or as multipass membrane proteins 2 Some other integral membrane proteins are called monotopic meaning that they are also permanently attached to the membrane but do not pass through it 3 Contents 1 Types 1 1 Classification by structure 1 2 Classification by topology 2 3D structure 3 Thermodynamic stability and folding 3 1 Stability of alpha helical transmembrane proteins 3 2 Folding of a helical transmembrane proteins 3 3 Stability and folding of beta barrel transmembrane proteins 4 3D structures 4 1 Light absorption driven transporters 4 2 Oxidoreduction driven transporters 4 3 Electrochemical potential driven transporters 4 4 P P bond hydrolysis driven transporters 4 5 Porters uniporters symporters antiporters 4 6 Alpha helical channels including ion channels 4 7 Enzymes 4 8 Proteins with alpha helical transmembrane anchors 4 9 Beta barrels composed of a single polypeptide chain 4 10 Beta barrels composed of several polypeptide chains 5 See also 6 ReferencesTypes editClassification by structure edit There are two basic types of transmembrane proteins 4 alpha helical and beta barrels Alpha helical proteins are present in the inner membranes of bacterial cells or the plasma membrane of eukaryotic cells and sometimes in the bacterial outer membrane 5 This is the major category of transmembrane proteins In humans 27 of all proteins have been estimated to be alpha helical membrane proteins 6 Beta barrel proteins are so far found only in outer membranes of gram negative bacteria cell walls of gram positive bacteria outer membranes of mitochondria and chloroplasts or can be secreted as pore forming toxins All beta barrel transmembrane proteins have simplest up and down topology which may reflect their common evolutionary origin and similar folding mechanism citation needed In addition to the protein domains there are unusual transmembrane elements formed by peptides A typical example is gramicidin A a peptide that forms a dimeric transmembrane b helix 7 This peptide is secreted by gram positive bacteria as an antibiotic A transmembrane polyproline II helix has not been reported in natural proteins Nonetheless this structure was experimentally observed in specifically designed artificial peptides 8 Classification by topology edit This classification refers to the position of the protein N and C termini on the different sides of the lipid bilayer Types I II III and IV are single pass molecules Type I transmembrane proteins are anchored to the lipid membrane with a stop transfer anchor sequence and have their N terminal domains targeted to the endoplasmic reticulum ER lumen during synthesis and the extracellular space if mature forms are located on cell membranes Type II and III are anchored with a signal anchor sequence with type II being targeted to the ER lumen with its C terminal domain while type III have their N terminal domains targeted to the ER lumen Type IV is subdivided into IV A with their N terminal domains targeted to the cytosol and IV B with an N terminal domain targeted to the lumen 9 The implications for the division in the four types are especially manifest at the time of translocation and ER bound translation when the protein has to be passed through the ER membrane in a direction dependent on the type citation needed nbsp Group I and II transmembrane proteins have opposite final topologies Group I proteins have the N terminus on the far side and C terminus on the cytosolic side Group II proteins have the C terminus on the far side and N terminus in the cytosol However final topology not the only criterion for defining transmembrane protein groups rather location of topogenic determinants and mechanism of assembly is considered in the classification 10 3D structure edit nbsp Increase in the number of 3D structures of membrane proteins knownMembrane protein structures can be determined by X ray crystallography electron microscopy or NMR spectroscopy 11 The most common tertiary structures of these proteins are transmembrane helix bundle and beta barrel The portion of the membrane proteins that are attached to the lipid bilayer see annular lipid shell consist mostly of hydrophobic amino acids 12 Membrane proteins which have hydrophobic surfaces are relatively flexible and are expressed at relatively low levels This creates difficulties in obtaining enough protein and then growing crystals Hence despite the significant functional importance of membrane proteins determining atomic resolution structures for these proteins is more difficult than globular proteins 13 As of January 2013 less than 0 1 of protein structures determined were membrane proteins despite being 20 30 of the total proteome 14 Due to this difficulty and the importance of this class of proteins methods of protein structure prediction based on hydropathy plots the positive inside rule and other methods have been developed 15 16 17 Thermodynamic stability and folding editStability of alpha helical transmembrane proteins edit Transmembrane alpha helical a helical proteins are unusually stable judging from thermal denaturation studies because they do not unfold completely within the membranes the complete unfolding would require breaking down too many a helical H bonds in the nonpolar media On the other hand these proteins easily misfold due to non native aggregation in membranes transition to the molten globule states formation of non native disulfide bonds or unfolding of peripheral regions and nonregular loops that are locally less stable citation needed It is also important to properly define the unfolded state The unfolded state of membrane proteins in detergent micelles is different from that in the thermal denaturation experiments citation needed This state represents a combination of folded hydrophobic a helices and partially unfolded segments covered by the detergent For example the unfolded bacteriorhodopsin in SDS micelles has four transmembrane a helices folded while the rest of the protein is situated at the micelle water interface and can adopt different types of non native amphiphilic structures Free energy differences between such detergent denatured and native states are similar to stabilities of water soluble proteins lt 10 kcal mol citation needed Folding of a helical transmembrane proteins edit Refolding of a helical transmembrane proteins in vitro is technically difficult There are relatively few examples of the successful refolding experiments as for bacteriorhodopsin In vivo all such proteins are normally folded co translationally within the large transmembrane translocon The translocon channel provides a highly heterogeneous environment for the nascent transmembrane a helices A relatively polar amphiphilic a helix can adopt a transmembrane orientation in the translocon although it would be at the membrane surface or unfolded in vitro because its polar residues can face the central water filled channel of the translocon Such mechanism is necessary for incorporation of polar a helices into structures of transmembrane proteins The amphiphilic helices remain attached to the translocon until the protein is completely synthesized and folded If the protein remains unfolded and attached to the translocon for too long it is degraded by specific quality control cellular systems citation needed Stability and folding of beta barrel transmembrane proteins edit Stability of beta barrel b barrel transmembrane proteins is similar to stability of water soluble proteins based on chemical denaturation studies Some of them are very stable even in chaotropic agents and high temperature Their folding in vivo is facilitated by water soluble chaperones such as protein Skp It is thought that b barrel membrane proteins come from one ancestor even having different number of sheets which could be added or doubled during evolution Some studies show a huge sequence conservation among different organisms and also conserved amino acids which hold the structure and help with folding 18 3D structures editSee also Transporter Classification Database Light absorption driven transporters edit Bacteriorhodopsin like proteins including rhodopsin see also opsin Bacterial photosynthetic reaction centres and photosystems I and II Light harvesting complexes from bacteria and chloroplastsOxidoreduction driven transporters edit Transmembrane cytochrome b like proteins coenzyme Q cytochrome c reductase cytochrome bc1 cytochrome b6f complex formate dehydrogenase respiratory nitrate reductase succinate coenzyme Q reductase fumarate reductase and succinate dehydrogenase See electron transport chain Cytochrome c oxidases from bacteria and mitochondriaElectrochemical potential driven transporters edit Proton or sodium translocating F type and V type ATPasesP P bond hydrolysis driven transporters edit P type calcium ATPase five different conformations Calcium ATPase regulators phospholamban and sarcolipin ABC transporters General secretory pathway Sec translocon preprotein translocase SecY Porters uniporters symporters antiporters edit Mitochondrial carrier proteins Major Facilitator Superfamily Glycerol 3 phosphate transporter Lactose permease and Multidrug transporter EmrD Resistance nodulation cell division multidrug efflux transporter AcrB see multidrug resistance Dicarboxylate amino acid cation symporter proton glutamate symporter Monovalent cation proton antiporter Sodium proton antiporter 1 NhaA Neurotransmitter sodium symporter Ammonia transporters Drug Metabolite Transporter small multidrug resistance transporter EmrE the structures are retracted as erroneous Alpha helical channels including ion channels edit Voltage gated ion channel like including potassium channels KcsA and KvAP and inward rectifier potassium ion channel Kirbac Large conductance mechanosensitive channel MscL Small conductance mechanosensitive ion channel MscS CorA metal ion transporters Ligand gated ion channel of neurotransmitter receptors acetylcholine receptor Aquaporins Chloride channels Outer membrane auxiliary proteins polysaccharide transporter a helical transmembrane proteins from the outer bacterial membraneEnzymes edit Methane monooxygenase Rhomboid protease Disulfide bond formation protein DsbA DsbB complex Proteins with alpha helical transmembrane anchors edit T cell receptor transmembrane dimerization domain Cytochrome c nitrite reductase complex Steryl sulfate sulfohydrolase Stannin Glycophorin A dimer Inovirus filamentous phage major coat protein Pilin Pulmonary surfactant associated protein Monoamine oxidases A and B Fatty acid amide hydrolase 19 Cytochrome P450 oxidases Corticosteroid 11b dehydrogenases Signal Peptide Peptidase Membrane protease specific for a stomatin homologBeta barrels composed of a single polypeptide chain edit Beta barrels from eight beta strands and with shear number of ten n 8 S 10 They include OmpA like transmembrane domain OmpA Virulence related outer membrane protein family OmpX Outer membrane protein W family OmpW Antimicrobial peptide resistance and lipid A acylation protein family PagP Lipid A deacylase PagL Opacity family porins NspA Autotransporter domain n 12 S 14 FadL outer membrane protein transport family including Fatty acid transporter FadL n 14 S 14 General bacterial porin family known as trimeric porins n 16 S 20 Maltoporin or sugar porins n 18 S 22 Nucleoside specific porin n 12 S 16 Outer membrane phospholipase A1 n 12 S 16 TonB dependent receptors and their plug domain They are ligand gated outer membrane channels n 22 S 24 including cobalamin transporter BtuB Fe III pyochelin receptor FptA receptor FepA ferric hydroxamate uptake receptor FhuA transporter FecA and pyoverdine receptor FpvA Outer membrane protein OpcA family n 10 S 12 that includes outer membrane protease OmpT and adhesin invasin OpcA protein Outer membrane protein G porin family n 14 S 16 Note n and S are respectively the number of beta strands and the shear number 20 of the beta barrel Beta barrels composed of several polypeptide chains edit Trimeric autotransporter n 12 S 12 Outer membrane efflux proteins also known as trimeric outer membrane factors n 12 S 18 including TolC and multidrug resistance proteins MspA porin octamer n S 16 and a hemolysin heptamer n S 14 These proteins are secreted See also editMembrane topology Transmembrane domain Transmembrane receptorsReferences edit Manor Joshua Feldblum Esther S Arkin Isaiah T 2012 Environment Polarity in Proteins Mapped Noninvasively by FTIR Spectroscopy The Journal of Physical Chemistry Letters 3 7 939 944 doi 10 1021 jz300150v PMC 3341589 PMID 22563521 Alberts Bruce Johnson Alexander Lewis Julian Raff Martin Roberts Keith Walter Peter 2002 Membrane Proteins Molecular Biology of the Cell 4th edition Garland Science Retrieved 31 October 2023 Steven R Goodman 2008 Medical cell biology Academic Press pp 37 ISBN 978 0 12 370458 0 Retrieved 24 November 2010 Jin Xiong 2006 Essential bioinformatics Cambridge University Press pp 208 ISBN 978 0 521 84098 9 Retrieved 13 November 2010 alpha helical proteins in outer membranes include Stannin and certain lipoproteins and others Almen MS Nordstrom KJ Fredriksson R Schioth HB 2009 Mapping the human membrane proteome a majority of the human membrane proteins can be classified according to function and evolutionary origin BMC Biol 7 50 doi 10 1186 1741 7007 7 50 PMC 2739160 PMID 19678920 Nicholson L K Cross T A 1989 Gramicidin cation channel an experimental determination of the right handed helix sense and verification of beta type hydrogen bonding Biochemistry 28 24 9379 9385 doi 10 1021 bi00450a019 PMID 2482072 Kubyshkin Vladimir Grage Stephan L Ulrich Anne S Budisa Nediljko 2019 Bilayer thickness determines the alignment of model polyproline helices in lipid membranes Physical Chemistry Chemical Physics 21 40 22396 22408 Bibcode 2019PCCP 2122396K doi 10 1039 c9cp02996f PMID 31577299 Harvey Lodish etc Molecular Cell Biology Sixth edition p 546 Goder Veit Spiess Martin 31 August 2001 Topogenesis of membrane proteins determinants and dynamics FEBS Letters 504 3 87 93 doi 10 1016 S0014 5793 01 02712 0 PMID 11532438 Cross Timothy A Sharma Mukesh Yi Myunggi Zhou Huan Xiang 2011 Influence of Solubilizing Environments on Membrane Protein Structures Trends in Biochemical Sciences 36 2 117 125 doi 10 1016 j tibs 2010 07 005 PMC 3161620 PMID 20724162 White Stephen General Principle of Membrane Protein Folding and Stability Stephen White Laboratory Homepage 10 Nov 2009 web verification needed Carpenter Elisabeth P Beis Konstantinos Cameron Alexander D Iwata So October 2008 Overcoming the challenges of membrane protein crystallography Current Opinion in Structural Biology 18 5 581 586 doi 10 1016 j sbi 2008 07 001 PMC 2580798 PMID 18674618 Membrane Proteins of known 3D Structure Archived from the original on 2013 12 25 Retrieved 2016 05 01 Elofsson Arne Heijne Gunnar von 7 June 2007 Membrane Protein Structure Prediction versus Reality Annual Review of Biochemistry 76 1 125 140 CiteSeerX 10 1 1 332 4023 doi 10 1146 annurev biochem 76 052705 163539 PMID 17579561 Chen Chien Peter Rost Burkhard 2002 State of the art in membrane protein prediction Applied Bioinformatics 1 1 21 35 CiteSeerX 10 1 1 134 7424 PMID 15130854 Hopf Thomas A Colwell Lucy J Sheridan Robert Rost Burkhard Sander Chris Marks Debora S June 2012 Three Dimensional Structures of Membrane Proteins from Genomic Sequencing Cell 149 7 1607 1621 doi 10 1016 j cell 2012 04 012 PMC 3641781 PMID 22579045 Michalik Marcin Orwick Rydmark Marcella Habeck Michael Alva Vikram Arnold Thomas Linke Dirk Permyakov Eugene A 3 August 2017 An evolutionarily conserved glycine tyrosine motif forms a folding core in outer membrane proteins PLOS ONE 12 8 e0182016 Bibcode 2017PLoSO 1282016M doi 10 1371 journal pone 0182016 PMC 5542473 PMID 28771529 Bracey MH Hanson MA Masuda KR Stevens RC Cravatt BF November 2002 Structural adaptations in a membrane enzyme that terminates endocannabinoid signaling Science 298 5599 1793 6 Bibcode 2002Sci 298 1793B doi 10 1126 science 1076535 PMID 12459591 S2CID 22656813 Murzin AG Lesk AM Chothia C March 1994 Principles determining the structure of beta sheet barrels in proteins I A theoretical analysis J Mol Biol 236 5 1369 81 doi 10 1016 0022 2836 94 90064 7 PMID 8126726 Retrieved from https en wikipedia org w index php title Transmembrane protein amp oldid 1191990209, wikipedia, wiki, book, books, library,

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