title: A conformational switch in the active site of BT_2972, a methyltransferase from an antibiotic resistant pathogen B. thetaiotaomicron.
abstract: Methylation is one of the most common biochemical reactions involved in cellular and metabolic functions and is catalysed by the action of methyltransferases. Bacteroides thetaiotaomicron is an antibiotic-resistant bacterium that confers resistance through methylation, and as yet, there is no report on the structure of methyltransferases from this bacterium. Here, we report the crystal structure of an AdoMet-dependent methyltransferase, BT_2972 and its complex with AdoMet and AdoHcy for B. thetaiotaomicron VPI-5482 strain along with isothermal titration calorimetric assessment of the binding affinities. Comparison of the apo and complexed BT_2972 structures reveals a significant conformational change between open and closed forms of the active site that presumably regulates the association with cofactors and may aid interaction with substrate. Together, our analysis suggests that BT_2972 is a small molecule methyltransferase and might catalyze two O-methylation reaction steps involved in the ubiquinone biosynthesis pathway.
authors.affiliation: Department of Biological Sciences, National University of Singapore, Singapore, Singapore.
authors.forename: Veerendra
authors.initials: V
authors.lastname: Kumar
authors.forename: J
authors.initials: J
authors.lastname: Sivaraman
mesh_terms: D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001439:Bacteroides / Q000187:drug effects* / Q000201:enzymology*; D002151:Calorimetry; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D024881:Drug Resistance, Bacterial / Q000187:drug effects*; D008780:Methyltransferases / Q000737:chemistry* / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D012435:S-Adenosylhomocysteine / Q000737:chemistry / Q000378:metabolism; D012436:S-Adenosylmethionine / Q000737:chemistry / Q000378:metabolism; D020539:Sequence Analysis, Protein; D040681:Structural Homology, Protein; D013329:Structure-Activity Relationship; D013379:Substrate Specificity / Q000187:drug effects; D013816:Thermodynamics
chemical_list: D000900:Anti-Bacterial Agents; D012436:S-Adenosylmethionine; D012435:S-Adenosylhomocysteine; D008780:Methyltransferases