title: Reinvestigation of the catalytic mechanism of formyl-CoA transferase, a class III CoA-transferase.
abstract: Formyl-coenzyme A transferase from Oxalobacter formigenes belongs to the Class III coenzyme A transferase family and catalyzes the reversible transfer of a CoA carrier between formyl-CoA and oxalate, forming oxalyl-CoA and formate. Formyl-CoA transferase has a unique three-dimensional fold composed of two interlaced subunits locked together like rings of a chain. We here present an intermediate in the reaction, formyl-CoA transferase containing the covalent beta-aspartyl-CoA thioester, adopting different conformations in the two active sites of the dimer, which was identified through crystallographic freeze-trapping experiments with formyl-CoA and oxalyl-CoA in the absence of acceptor carboxylic acid. The formation of the enzyme-CoA thioester was also confirmed by mass spectrometric data. Further structural data include a trapped aspartyl-formyl anhydride protected by a glycine loop closing down over the active site. In a crystal structure of the beta-aspartyl-CoA thioester of an inactive mutant variant, oxalate was found bound to the open conformation of the glycine loop. Together with hydroxylamine trapping experiments and kinetic as well as mutagenesis data, the structures of these formyl-CoA transferase complexes provide new information on the Class III CoA-transferase family and prompt redefinition of the catalytic steps and the modified reaction mechanism of formyl-CoA transferase proposed here.
authors.affiliation: Department of Medical Biochemistry and Biophysics, Molecular Structural Biology, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Catrine L
authors.initials: CL
authors.lastname: Berthold
authors.forename: Cory G
authors.initials: CG
authors.lastname: Toyota
authors.forename: Nigel G J
authors.initials: NG
authors.lastname: Richards
authors.forename: Ylva
authors.initials: Y
authors.lastname: Lindqvist
mesh_terms: D000214:Acyl Coenzyme A / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D015256:Coenzyme A-Transferases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D019281:Dimerization; D007700:Kinetics; D009154:Mutation; D010070:Oxalates / Q000737:chemistry / Q000378:metabolism; D020624:Oxalobacter formigenes / Q000201:enzymology* / Q000235:genetics; D017510:Protein Folding; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary
chemical_list: D000214:Acyl Coenzyme A; D001426:Bacterial Proteins; D010070:Oxalates; C523110:oxalyl-coenzyme A; C106238:formyl-coenzyme A; D015256:Coenzyme A-Transferases; C064813:formyl-coenzyme A transferase