Cobalamin-independent methionine synthase (MetE): a face-to-face double barrel that evolved by gene duplication.

ABSTRACT: Cobalamin-independent methionine synthase (MetE) catalyzes the transfer of a methyl group from methyltetrahydrofolate to L-homocysteine (Hcy) without using an intermediate methyl carrier. Although MetE displays no detectable sequence homology with cobalamin-dependent methionine synthase (MetH), both enzymes require zinc for activation and binding of Hcy. Crystallographic analyses of MetE from T. maritima reveal an unusual dual-barrel structure in which the active site lies between the tops of the two (betaalpha)(8) barrels. The fold of the N-terminal barrel confirms that it has evolved from the C-terminal polypeptide by gene duplication; comparisons of the barrels provide an intriguing example of homologous domain evolution in which binding sites are obliterated. The C-terminal barrel inco

SUBMITTER: Pejchal R 

PROVIDER: S-EPMC539065 | biostudies-literature | 2005 Feb

REPOSITORIES: biostudies-literature