Crystal Structure of Mesaconyl-CoA Hydratase from CM4.

, a facultative methylotroph, assimilates C compounds and accumulates poly-β-hydroxylbutyrate (PHB) as carbon and energy sources. The ethylmalonyl pathway is central to the carbon metabolism of , and is linked with a serine cycle and a PHB biosynthesis pathway. Understanding the ethylmalonyl pathway is vital in utilizing methylotrophs to produce value-added chemicals. In this study, we determined the crystal structure of the mesaconyl-CoA hydratase from (MeaC) that catalyzes the reversible conversion of mesaconyl-CoA to β-methylmalyl-CoA. The crystal structure of MeaC revealed that the enzyme belongs to the MaoC-like dehydratase domain superfamily and functions as a trimer. In our current MeaC structure, malic acid occupied the substrate binding site, which reveals how MeaC recognizes the β-methylmalyl-moiety of its substrate. The active site of the enzyme was further speculated by comparing its structure with those of other MaoC-like hydratases.