The antenna complex in purple photosynthetic bacteria are protein complexes[1] responsible for the transfer of solar energy to the photosynthetic reaction centre.[2] Purple bacteria, particularly Rhodopseudomonas acidophila of purple non-sulfur bacteria, have been one of the main groups of organisms used to study bacterial antenna complexes so much is known about this group's photosynthetic components.[3] It is one of the many independent types of light-harvesting complex used by various photosynthetic organisms.
In photosynthetic purple bacteria there are usually two antenna complexes that are generally composed of two types of polypeptides (alpha and beta chains).[4][5][2] These proteins are arranged in a ring-like fashion creating a cylinder that spans the membrane; the proteins bind two or three types of bacteriochlorophyll (BChl) molecules and different types of carotenoids depending on the species.[4][5] LH2 is the outer antenna complex that spans the membrane. It is peripheral to LH1, an antenna complex (also known as the core antenna complex) that is directly associated with the reaction centre,[2][3][6] with the RC at the center of its elliptical ring.[7] Unlike for LH1 complexes, the amount of LH2 complexes present vary with growth conditions and light intensity.[2]
Both the alpha and the beta chains of antenna complexes are small proteins of 42 to 68 residues which share a three-domain organization. They are composed of a N-terminal hydrophiliccytoplasmic domain followed by a transmembrane region and a C-terminal hydrophilic periplasmic domain. In the transmembrane region of both chains there is a conserved histidine which is most probably involved in the binding of the magnesium atom of a bacteriochlorophyll group. The beta chains contain an additional conserved histidine which is located at the C-terminal extremity of the cytoplasmic domain and which is also thought to be involved in bacteriochlorophyll-binding.
The particular chemical environment of the Bchl molecules influences the wavelength of light they are able to absorb.[2][6] LH2 complexes of R. acidophils have BChl a molecules that absorb at 850 nm and 800 nm respectively.[2][6] BChl a molecules that absorb at 850 nm are present in a hydrophobic environment.[2][6] These pigments are in contact with a number of non-polar, hydrophobic residues.[6] BChl a molecules that absorb at 800 nm are present in a relatively polar environment.[2][6] The formylated N-terminus of the alpha polypeptide, a nearby histidine, and a water molecule are responsible for this.[2]
^ abKoepke J, Hu X, Muenke C, Schulten K, Michel H (May 1996). "The crystal structure of the light-harvesting complex II (B800-850) from Rhodospirillum molischianum". Structure. 4 (5): 581–97. doi:10.1016/S0969-2126(96)00063-9. PMID 8736556.
^ abcdefghiKühlbrandt, Werner (June 1995). "Structure and function of bacterial light-harvesting complexes". Structure. 3 (6): 521–525. doi:10.1016/S0969-2126(01)00184-8. PMID 8590011.
^ abCodgell, Richard J.; Isaacs, Neil W.; Howard, Tina D.; McLuskey, Karen; Niall, J. Fraser; Prince, Stephen M. (July 1999). "How photosynthetic bacteria harvest solar energy". Journal of Bacteriology. 181 (13): 3869–3879. doi:10.1128/JB.181.13.3869-3879.1999. PMC93873. PMID 10383951.
^ abWagner-Huber R, Brunisholz RA, Bissig I, Frank G, Suter F, Zuber H (1992). "The primary structure of the antenna polypeptides of Ectothiorhodospira halochloris and Ectothiorhodospira halophila. Four core-type antenna polypeptides in E. halochloris and E. halophila". Eur. J. Biochem. 205 (3): 917–925. doi:10.1111/j.1432-1033.1992.tb16858.x. PMID 1577009.
^ abBrunisholz RA, Zuber H (1992). "Structure, function and organization of antenna polypeptides and antenna complexes from the three families of Rhodospirillaneae". J. Photochem. Photobiol. B. 15 (1): 113–140. doi:10.1016/1011-1344(92)87010-7. PMID 1460542.
^ abcdefMcDermott, G.; Prince, S. M.; Freer, A. A.; Hawthornthwaite-Lawless, A. M.; Papiz, M. Z.; Cogdell, R. J.; Isaacs, N. W. (1995-04-06). "Crystal structure of an integral membrane light-harvesting complex from photosynthetic bacteria". Nature. 374 (6522): 517–521. Bibcode:1995Natur.374..517M. doi:10.1038/374517a0. ISSN 1476-4687. S2CID 4258914.
^Gardiner, AT; Nguyen-Phan, TC; Cogdell, RJ (August 2020). "A comparative look at structural variation among RC-LH1 'Core' complexes present in anoxygenic phototrophic bacteria". Photosynthesis Research. 145 (2): 83–96. doi:10.1007/s11120-020-00758-3. PMC7423801. PMID 32430765.
May 02, 2024
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This article may be too technical for most readers to understand Please help improve it to make it understandable to non experts without removing the technical details June 2016 Learn how and when to remove this message The antenna complex in purple photosynthetic bacteria are protein complexes 1 responsible for the transfer of solar energy to the photosynthetic reaction centre 2 Purple bacteria particularly Rhodopseudomonas acidophila of purple non sulfur bacteria have been one of the main groups of organisms used to study bacterial antenna complexes so much is known about this group s photosynthetic components 3 It is one of the many independent types of light harvesting complex used by various photosynthetic organisms Antenna complex alpha beta subunitStructure of the light harvesting complex II 1 IdentifiersSymbolLHCPfamPF00556InterProIPR000066PROSITEPDOC00748SCOP21lgh SCOPe SUPFAMOPM superfamily2OPM protein1lghAvailable protein structures Pfam structures ECOD PDBRCSB PDB PDBe PDBjPDBsumstructure summary In photosynthetic purple bacteria there are usually two antenna complexes that are generally composed of two types of polypeptides alpha and beta chains 4 5 2 These proteins are arranged in a ring like fashion creating a cylinder that spans the membrane the proteins bind two or three types of bacteriochlorophyll BChl molecules and different types of carotenoids depending on the species 4 5 LH2 is the outer antenna complex that spans the membrane It is peripheral to LH1 an antenna complex also known as the core antenna complex that is directly associated with the reaction centre 2 3 6 with the RC at the center of its elliptical ring 7 Unlike for LH1 complexes the amount of LH2 complexes present vary with growth conditions and light intensity 2 Both the alpha and the beta chains of antenna complexes are small proteins of 42 to 68 residues which share a three domain organization They are composed of a N terminal hydrophilic cytoplasmic domain followed by a transmembrane region and a C terminal hydrophilic periplasmic domain In the transmembrane region of both chains there is a conserved histidine which is most probably involved in the binding of the magnesium atom of a bacteriochlorophyll group The beta chains contain an additional conserved histidine which is located at the C terminal extremity of the cytoplasmic domain and which is also thought to be involved in bacteriochlorophyll binding The particular chemical environment of the Bchl molecules influences the wavelength of light they are able to absorb 2 6 LH2 complexes of R acidophils have BChl a molecules that absorb at 850 nm and 800 nm respectively 2 6 BChl a molecules that absorb at 850 nm are present in a hydrophobic environment 2 6 These pigments are in contact with a number of non polar hydrophobic residues 6 BChl a molecules that absorb at 800 nm are present in a relatively polar environment 2 6 The formylated N terminus of the alpha polypeptide a nearby histidine and a water molecule are responsible for this 2 Subfamilies editAntenna complex alpha subunit InterPro IPR002361 Antenna complex beta subunit InterPro IPR002362References edit a b Koepke J Hu X Muenke C Schulten K Michel H May 1996 The crystal structure of the light harvesting complex II B800 850 from Rhodospirillum molischianum Structure 4 5 581 97 doi 10 1016 S0969 2126 96 00063 9 PMID 8736556 a b c d e f g h i Kuhlbrandt Werner June 1995 Structure and function of bacterial light harvesting complexes Structure 3 6 521 525 doi 10 1016 S0969 2126 01 00184 8 PMID 8590011 a b Codgell Richard J Isaacs Neil W Howard Tina D McLuskey Karen Niall J Fraser Prince Stephen M July 1999 How photosynthetic bacteria harvest solar energy Journal of Bacteriology 181 13 3869 3879 doi 10 1128 JB 181 13 3869 3879 1999 PMC 93873 PMID 10383951 a b Wagner Huber R Brunisholz RA Bissig I Frank G Suter F Zuber H 1992 The primary structure of the antenna polypeptides of Ectothiorhodospira halochloris and Ectothiorhodospira halophila Four core type antenna polypeptides in E halochloris and E halophila Eur J Biochem 205 3 917 925 doi 10 1111 j 1432 1033 1992 tb16858 x PMID 1577009 a b Brunisholz RA Zuber H 1992 Structure function and organization of antenna polypeptides and antenna complexes from the three families of Rhodospirillaneae J Photochem Photobiol B 15 1 113 140 doi 10 1016 1011 1344 92 87010 7 PMID 1460542 a b c d e f McDermott G Prince S M Freer A A Hawthornthwaite Lawless A M Papiz M Z Cogdell R J Isaacs N W 1995 04 06 Crystal structure of an integral membrane light harvesting complex from photosynthetic bacteria Nature 374 6522 517 521 Bibcode 1995Natur 374 517M doi 10 1038 374517a0 ISSN 1476 4687 S2CID 4258914 Gardiner AT Nguyen Phan TC Cogdell RJ August 2020 A comparative look at structural variation among RC LH1 Core complexes present in anoxygenic phototrophic bacteria Photosynthesis Research 145 2 83 96 doi 10 1007 s11120 020 00758 3 PMC 7423801 PMID 32430765 Retrieved 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