title: Molecular Basis of C-N Bond Cleavage by the Glycyl Radical Enzyme Choline Trimethylamine-Lyase.
abstract: Deamination of choline catalyzed by the glycyl radical enzyme choline trimethylamine-lyase (CutC) has emerged as an important route for the production of trimethylamine, a microbial metabolite associated with both human disease and biological methane production. Here, we have determined five high-resolution X-ray structures of wild-type CutC and mechanistically informative mutants in the presence of choline. Within an unexpectedly polar active site, CutC orients choline through hydrogen bonding with a putative general base, and through close interactions between phenolic and carboxylate oxygen atoms of the protein scaffold and the polarized methyl groups of the trimethylammonium moiety. These structural data, along with biochemical analysis of active site mutants, support a mechanism that involves direct elimination of trimethylamine. This work broadens our understanding of radical-based enzyme catalysis and will aid in the rational design of inhibitors of bacterial trimethylamine production.
authors.affiliation: Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138, USA.
authors.forename: Smaranda
authors.initials: S
authors.lastname: Bodea
authors.affiliation: Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts, Avenue 68-680, Cambridge, MA 02139, USA.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Funk
authors.affiliation: Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138, USA. Electronic address: balskus@chemistry.harvard.edu.
authors.forename: Emily P
authors.initials: EP
authors.lastname: Balskus
authors.affiliation: Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts, Avenue 68-680, Cambridge, MA 02139, USA; Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Center for Environmental Health Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. Electronic address: cdrennan@mit.edu.
authors.forename: Catherine L
authors.initials: CL
authors.lastname: Drennan
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D020134:Catalytic Domain; D002794:Choline / Q000378:metabolism; D018360:Crystallography, X-Ray; D003901:Desulfovibrio / Q000737:chemistry / Q000201:enzymology* / Q000378:metabolism; D006860:Hydrogen Bonding; D008190:Lyases / Q000737:chemistry* / Q000378:metabolism; D008744:Methylamines / Q000378:metabolism*; D008958:Models, Molecular; D011487:Protein Conformation; D013379:Substrate Specificity
chemical_list: D001426:Bacterial Proteins; D008744:Methylamines; D008190:Lyases; C023336:trimethylamine; D002794:Choline