Methylthiotransferases are enzymes of the radical S-adenosyl methionine (radical SAM) superfamily. These enzymes catalyze the addition of a methylthio group to various biochemical compounds including tRNA and proteins.[1] Methylthiotransferases are classified into one of four classes based on their substrates and mechanisms.[2] All methylthiotransferases have been shown to contain two Fe-S clusters, one canonical cluster and one auxiliary cluster, that both function in the addition of the methylthio group to the substrate.[3]
Methylthiotransferases, also known as MTTases, are a subset of the radical SAM enzyme superfamily. These enzymes catalyze the addition of a methylthio group to either a protein or tRNA substrate.[1] Radical S-adenosylmethionine enzymes, otherwise known as radical SAM enzymes, are metalloproteins that cleave S-adenosyl-L-methionine into L-methionine and a 5'-deoxyadenosyl 5'-radical (5'-dA).[3] 5'-dA is an intermediate in the reactions catalyzed by radical SAMs. 5'-dA removes a hydrogen from the substrate and allows for the addition of another group to that carbon on the substrate.[3] In order to complete their reactions, all radical SAMs require a reduced [4Fe-4S] cluster, which is found through a conserved cysteine motif, CX3CX2C.[3] Radical SAMs can have one or multiple Fe-S clusters. In this case, methylthiotransferases have multiple clusters. Radical SAMs are involved in many cellular processes in all three domains of life including metabolism and the biosynthesis of many cofactors used within the cell.[3]
There are four known classes of Methylthiotransferases; three classes are involved in the methylthiolation of tRNAs and one is involved in the methylthiolation of proteins.[2] All identified methylthiotransferases have two Fe-S active clusters and three characteristic domains within the protein.[1][2] These three structural domains include an N-terminal uncharacterized protein family 0004 (UPF0004) domain that contains the auxiliary Fe-S cluster, a central radical SAM motif that contains the central active Fe-S motif, and a C-terminal "TRAM" domain that is thought to be involved in substrate recognition.[1][2] Of the two Fe-S clusters, the central cluster binds the SAM that is used to generate the 5'-dA while the auxiliary cluster has a less studied functionality. Most research suggests that this auxiliary cluster functions as the direct donor of the sulfur during catalysis or it functions to coordinate an exogenous source of sulfur for use during catalysis.[4] In the comparatively well studied methylthiotransferase MiaB, the auxiliary cluster is thought to directly donate the sulfur of the methylthio group during catalysis.[4]
Proposed mechanismedit
Methylthiotransferases catalyze the addition of a methylthio group to various biochemical products. Transferring methylthio groups is a complicated reaction requiring multiple Fe-S clusters. Previous literature proposed that the enzymes would function sequentially, first adding a sulfur to the substrate and then adding a methyl group derived from the second SAM molecule.[5] This mechanism has not been supported by recent works. Studies now propose that a methyl group from the first SAM molecule is transferred to a sulfur within the auxiliary [4Fe-4S] cluster to form a methylthio group that is then transferred to the product via a radical mechanism facilitated by the 5'-dA radical intermediate produced from the cleavage of the second SAM molecule.[4][6] The proposed mechanisms for MiaB and RimO slightly differ, with MiaB using a coordinated sulfur as the methylthio group[4] and RimO using an external sulfur attached to the unique iron atom within the cluster as the methylthio group.[6] Despite this difference, both use the same basic principles for the mechanism; create a methylthiolated intermediate using the auxiliary [4Fe-4S] cluster and then add the methylthio group to the substrate.[4][6]
Known examplesedit
Formation of the [3Fe-4S]0 auxiliary cluster of MiaB via the nucleophilic attack of a μ3-bridging sulfide. Adapted from Zhang et al. 2020.
MiaBedit
MiaB is a methylthiotransferase that completes the methylthiolation of a modified adenosine base, N6-isopentenyl adenosine to C2-methylthio-N6-isopentenyl adenosine, in tRNA which involves the addition of a methylthiogroup to an inactivate C-H bond.[1][3][4] The modification of this base in tRNAs enhances codon-anticodon binding and maintenance of the ribosomal reading frame during translation of an mRNA into protein.[4] Unlike the other methylthiotransferases described here, MiaB donates the sulfur group for methylthiolation itself instead of using a secondary sulfur donor and also completes two SAM-dependent reactions within a single polypeptide.[3]
MtaBedit
MtaB is a methylthiotransferase that exists in bacteria, archaea, and eukarya that completes the methylthiolation of the modified adenosine base, N6-threonylcarbamoyladenosine, at position 37 of tRNAs that code for the ANN codons to 2-methylthio-N6-threonylcarbamoyladenosine.[1][7] When compared to MiaB and RimO, MtaB is much less studied but is still potentially involved in various cellular processes. One potential application of studying this specific MTTase is that it is encoded by the gene CDKAL1 in humans, which is known to increase the reduction of insulin secretion when mutated or downregulated thus leading to a higher risk of the person developing type 2 diabetes.[1][7]
RimOedit
Mechanism of RimO catalyzed addition of a methylthio group to the β-carbon of aspartate. Adapted from Landgraf et al. 2013.
RimO is a methylthiotransferase that completes the methylthiolation of the β-carbon of the Asp88 residue of the ribosomal S12 protein in bacteria, specifically E. coli.[1][2] This MTTase is the first identified to create post-translational modifications as all other previously identified MTTases modify tRNAs. Though RimO acts on a different substrate than the other classes of MTTases, the primary structure of the protein and the mechanism behind its action are relatively similar.[1]
Referencesedit
^ abcdefghiWang, Jiarui; Woldring, Rory P.; Román-Meléndez, Gabriel D.; McClain, Alan M.; Alzua, Brian R.; Marsh, E. Neil G. (2014-09-19). "Recent Advances in Radical SAM Enzymology: New Structures and Mechanisms". ACS Chemical Biology. 9 (9): 1929–1938. doi:10.1021/cb5004674. ISSN 1554-8929. PMC4168785. PMID 25009947.
^ abcdeLee, Kyung-Hoon; Saleh, Lana; Anton, Brian P.; Madinger, Catherine L.; Benner, Jack S.; Iwig, David F.; Roberts, Richard J.; Krebs, Carsten; Booker, Squire J. (2009-10-27). "Characterization of RimO, a New Member of the Methylthiotransferase Subclass of the Radical SAM Superfamily". Biochemistry. 48 (42): 10162–10174. doi:10.1021/bi900939w. ISSN 0006-2960. PMC2952840. PMID 19736993.
^ abcdefgBooker, Squire J; Cicchillo, Robert M; Grove, Tyler L (2007). "Self-sacrifice in radical S-adenosylmethionine proteins". Current Opinion in Chemical Biology. 11 (5): 543–552. doi:10.1016/j.cbpa.2007.08.028. PMC2637762. PMID 17936058.
^ abcdefgZhang, Bo; Arcinas, Arthur J.; Radle, Matthew I.; Silakov, Alexey; Booker, Squire J.; Krebs, Carsten (2020-01-29). "First Step in Catalysis of the Radical S-Adenosylmethionine Methylthiotransferase MiaB Yields an Intermediate with a [3Fe-4S]0-Like Auxiliary Cluster". Journal of the American Chemical Society. 142 (4): 1911–1924. doi:10.1021/jacs.9b11093. ISSN 0002-7863. PMC7008301. PMID 31899624.
^Fontecave, M.; Mulliez, E.; Atta, M. (2008-03-21). "New Light on Methylthiolation Reactions". Chemistry & Biology. 15 (3): 209–210. doi:10.1016/j.chembiol.2008.02.011. ISSN 1074-5521. PMID 18355719.
^ abcLandgraf, Bradley J.; Arcinas, Arthur J.; Lee, Kyung-Hoon; Booker, Squire J. (2013-10-16). "Identification of an Intermediate Methyl Carrier in the Radical S-Adenosylmethionine Methylthiotransferases RimO and MiaB". Journal of the American Chemical Society. 135 (41): 15404–15416. doi:10.1021/ja4048448. ISSN 0002-7863. PMC4023531. PMID 23991893.
^ abArragain, Simon; Handelman, Samuel K.; Forouhar, Farhad; Wei, Fan-Yan; Tomizawa, Kazuhito; Hunt, John F.; Douki, Thierry; Fontecave, Marc; Mulliez, Etienne; Atta, Mohamed (2010-09-10). "Identification of Eukaryotic and Prokaryotic Methylthiotransferase for Biosynthesis of 2-Methylthio- N 6 -threonylcarbamoyladenosine in tRNA". Journal of Biological Chemistry. 285 (37): 28425–28433. doi:10.1074/jbc.M110.106831. ISSN 0021-9258. PMC2937867. PMID 20584901.
January 01, 1970
methylthiotransferase, enzymes, radical, adenosyl, methionine, radical, superfamily, these, enzymes, catalyze, addition, methylthio, group, various, biochemical, compounds, including, trna, proteins, classified, into, four, classes, based, their, substrates, m. Methylthiotransferases are enzymes of the radical S adenosyl methionine radical SAM superfamily These enzymes catalyze the addition of a methylthio group to various biochemical compounds including tRNA and proteins 1 Methylthiotransferases are classified into one of four classes based on their substrates and mechanisms 2 All methylthiotransferases have been shown to contain two Fe S clusters one canonical cluster and one auxiliary cluster that both function in the addition of the methylthio group to the substrate 3 Contents 1 Overview 2 Proposed mechanism 3 Known examples 3 1 MiaB 3 2 MtaB 3 3 RimO 4 ReferencesOverview editMethylthiotransferases also known as MTTases are a subset of the radical SAM enzyme superfamily These enzymes catalyze the addition of a methylthio group to either a protein or tRNA substrate 1 Radical S adenosylmethionine enzymes otherwise known as radical SAM enzymes are metalloproteins that cleave S adenosyl L methionine into L methionine and a 5 deoxyadenosyl 5 radical 5 dA 3 5 dA is an intermediate in the reactions catalyzed by radical SAMs 5 dA removes a hydrogen from the substrate and allows for the addition of another group to that carbon on the substrate 3 In order to complete their reactions all radical SAMs require a reduced 4Fe 4S cluster which is found through a conserved cysteine motif CX3CX2C 3 Radical SAMs can have one or multiple Fe S clusters In this case methylthiotransferases have multiple clusters Radical SAMs are involved in many cellular processes in all three domains of life including metabolism and the biosynthesis of many cofactors used within the cell 3 There are four known classes of Methylthiotransferases three classes are involved in the methylthiolation of tRNAs and one is involved in the methylthiolation of proteins 2 All identified methylthiotransferases have two Fe S active clusters and three characteristic domains within the protein 1 2 These three structural domains include an N terminal uncharacterized protein family 0004 UPF0004 domain that contains the auxiliary Fe S cluster a central radical SAM motif that contains the central active Fe S motif and a C terminal TRAM domain that is thought to be involved in substrate recognition 1 2 Of the two Fe S clusters the central cluster binds the SAM that is used to generate the 5 dA while the auxiliary cluster has a less studied functionality Most research suggests that this auxiliary cluster functions as the direct donor of the sulfur during catalysis or it functions to coordinate an exogenous source of sulfur for use during catalysis 4 In the comparatively well studied methylthiotransferase MiaB the auxiliary cluster is thought to directly donate the sulfur of the methylthio group during catalysis 4 Proposed mechanism editMethylthiotransferases catalyze the addition of a methylthio group to various biochemical products Transferring methylthio groups is a complicated reaction requiring multiple Fe S clusters Previous literature proposed that the enzymes would function sequentially first adding a sulfur to the substrate and then adding a methyl group derived from the second SAM molecule 5 This mechanism has not been supported by recent works Studies now propose that a methyl group from the first SAM molecule is transferred to a sulfur within the auxiliary 4Fe 4S cluster to form a methylthio group that is then transferred to the product via a radical mechanism facilitated by the 5 dA radical intermediate produced from the cleavage of the second SAM molecule 4 6 The proposed mechanisms for MiaB and RimO slightly differ with MiaB using a coordinated sulfur as the methylthio group 4 and RimO using an external sulfur attached to the unique iron atom within the cluster as the methylthio group 6 Despite this difference both use the same basic principles for the mechanism create a methylthiolated intermediate using the auxiliary 4Fe 4S cluster and then add the methylthio group to the substrate 4 6 Known examples edit nbsp Formation of the 3Fe 4S 0 auxiliary cluster of MiaB via the nucleophilic attack of a m3 bridging sulfide Adapted from Zhang et al 2020 MiaB edit MiaB is a methylthiotransferase that completes the methylthiolation of a modified adenosine base N6 isopentenyl adenosine to C2 methylthio N6 isopentenyl adenosine in tRNA which involves the addition of a methylthiogroup to an inactivate C H bond 1 3 4 The modification of this base in tRNAs enhances codon anticodon binding and maintenance of the ribosomal reading frame during translation of an mRNA into protein 4 Unlike the other methylthiotransferases described here MiaB donates the sulfur group for methylthiolation itself instead of using a secondary sulfur donor and also completes two SAM dependent reactions within a single polypeptide 3 MtaB edit MtaB is a methylthiotransferase that exists in bacteria archaea and eukarya that completes the methylthiolation of the modified adenosine base N6 threonylcarbamoyladenosine at position 37 of tRNAs that code for the ANN codons to 2 methylthio N6 threonylcarbamoyladenosine 1 7 When compared to MiaB and RimO MtaB is much less studied but is still potentially involved in various cellular processes One potential application of studying this specific MTTase is that it is encoded by the gene CDKAL1 in humans which is known to increase the reduction of insulin secretion when mutated or downregulated thus leading to a higher risk of the person developing type 2 diabetes 1 7 RimO edit nbsp Mechanism of RimO catalyzed addition of a methylthio group to the b carbon of aspartate Adapted from Landgraf et al 2013 RimO is a methylthiotransferase that completes the methylthiolation of the b carbon of the Asp88 residue of the ribosomal S12 protein in bacteria specifically E coli 1 2 This MTTase is the first identified to create post translational modifications as all other previously identified MTTases modify tRNAs Though RimO acts on a different substrate than the other classes of MTTases the primary structure of the protein and the mechanism behind its action are relatively similar 1 References edit a b c d e f g h i Wang Jiarui Woldring Rory P Roman Melendez Gabriel D McClain Alan M Alzua Brian R Marsh E Neil G 2014 09 19 Recent Advances in Radical SAM Enzymology New Structures and Mechanisms ACS Chemical Biology 9 9 1929 1938 doi 10 1021 cb5004674 ISSN 1554 8929 PMC 4168785 PMID 25009947 a b c d e Lee Kyung Hoon Saleh Lana Anton Brian P Madinger Catherine L Benner Jack S Iwig David F Roberts Richard J Krebs Carsten Booker Squire J 2009 10 27 Characterization of RimO a New Member of the Methylthiotransferase Subclass of the Radical SAM Superfamily Biochemistry 48 42 10162 10174 doi 10 1021 bi900939w ISSN 0006 2960 PMC 2952840 PMID 19736993 a b c d e f g Booker Squire J Cicchillo Robert M Grove Tyler L 2007 Self sacrifice in radical S adenosylmethionine proteins Current Opinion in Chemical Biology 11 5 543 552 doi 10 1016 j cbpa 2007 08 028 PMC 2637762 PMID 17936058 a b c d e f g Zhang Bo Arcinas Arthur J Radle Matthew I Silakov Alexey Booker Squire J Krebs Carsten 2020 01 29 First Step in Catalysis of the Radical S Adenosylmethionine Methylthiotransferase MiaB Yields an Intermediate with a 3Fe 4S 0 Like Auxiliary Cluster Journal of the American Chemical Society 142 4 1911 1924 doi 10 1021 jacs 9b11093 ISSN 0002 7863 PMC 7008301 PMID 31899624 Fontecave M Mulliez E Atta M 2008 03 21 New Light on Methylthiolation Reactions Chemistry amp Biology 15 3 209 210 doi 10 1016 j chembiol 2008 02 011 ISSN 1074 5521 PMID 18355719 a b c Landgraf Bradley J Arcinas Arthur J Lee Kyung Hoon Booker Squire J 2013 10 16 Identification of an Intermediate Methyl Carrier in the Radical S Adenosylmethionine Methylthiotransferases RimO and MiaB Journal of the American Chemical Society 135 41 15404 15416 doi 10 1021 ja4048448 ISSN 0002 7863 PMC 4023531 PMID 23991893 a b Arragain Simon Handelman Samuel K Forouhar Farhad Wei Fan Yan Tomizawa Kazuhito Hunt John F Douki Thierry Fontecave Marc Mulliez Etienne Atta Mohamed 2010 09 10 Identification of Eukaryotic and Prokaryotic Methylthiotransferase for Biosynthesis of 2 Methylthio N 6 threonylcarbamoyladenosine in tRNA Journal of Biological Chemistry 285 37 28425 28433 doi 10 1074 jbc M110 106831 ISSN 0021 9258 PMC 2937867 PMID 20584901 Retrieved from https en wikipedia org w index php title Methylthiotransferase amp oldid 1170976601, wikipedia, wiki, book, books, library,
