Purification and characterization of a methanol-induced cobamide-containing protein from Sporomusa ovata

The major cobamide-containing protein from methanol-utilizing Sporomusa ovata was 8-fold enriched to apparent homogeneity. The protein exhibited a molecular mass of 40 kDa and of 38 kDa determined by gel filtration and by SDS-polyacrylamide gel electrophoresis, respectively. This finding indicates a monomeric protein structure. Monospecific polyclonal antisera raised against the protein did not cross react with another cobamide-containing protein from Sporomusa cells. Only the 40 kDa cobamide-containing protein was induced by methanol, since proteins from cells grown on 3,4-dimethoxybenzoate, betaine H₂/CO₂, or fructose showed faint or no cross reaction. Hence, the 40 kDa cobamide-containing protein is presumably involved in the methyltransfer reaction of the methanol metabolism. The purified enzyme revealed 1.1 mol of p-cresolyl cobamide per mol of protein, but it lacked of iron-sulfur centers. Remarkably, the cofactor was firmly bound to its protein.