Cobalamin-dependent methionine synthase: the structure of a methylcobalamin-binding fragment and implications for other B12-dependent enzymes.
Cobalamin-dependent methionine synthase is a large enzyme composed of structurally and functionally distinct regions. Recent studies have begun to define the roles of several regions of the protein. In particular, the structure of a 27 kDa cobalamin-binding fragment of the enzyme from Escherichia coli has been determined by X-ray crystallography, and has revealed the motifs and interactions responsible for recognition of the cofactor. The amino acid sequences of several adenosylcobalamin-dependent enzymes, the methylmalonyl coenzyme A mutases and glutamate mutases, show homology with the cobalamin-binding region of methionine synthase and retain conserved residues that are determinants for the binding of the prosthetic group, suggesting that these mutases and methionine synthase share common three-dimensional structures.
Drennan
C L
CL
Biophysics Research Division, University of Michigan, Ann Arbor 48109-1055.
Matthews
R G
RG
Ludwig
M L
ML
D013766:5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase / Q000737:chemistry* / Q000378:metabolism; D000591:Amino Acid Isomerases / Q000737:chemistry; D000595:Amino Acid Sequence; D001665:Binding Sites; D004926:Escherichia coli / Q000201:enzymology; D019751:Intramolecular Transferases; D008765:Methylmalonyl-CoA Mutase / Q000737:chemistry; D008969:Molecular Sequence Data; D011487:Protein Conformation; D014805:Vitamin B 12 / Q000031:analogs & derivatives* / Q000378:metabolism / Q000502:physiology
C019476:mecobalamin; D013766:5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase; D000591:Amino Acid Isomerases; D019751:Intramolecular Transferases; C021570:methylaspartate mutase; D008765:Methylmalonyl-CoA Mutase; D014805:Vitamin B 12