Amino acid sequence studies of the light subunit of methylamine dehydrogenase from Pseudomonas AM1: existence of two residues binding the prosthetic group.

The methylamine dehydrogenase from Pseudomonas AM1 is a tetramer composed of two subunits, light(L)- and heavy-subunits. The amino acid sequence of the L-subunit was determined by sequence analyses of trypsin, chymotrypsin, staphylococcal protease, and thermolysin peptides of Cm-protein. The subunit consisted of a single polypeptide chain of 129 amino acid residues, with alanine and serine at the amino(N)- and carboxyl(C)-terminus, respectively. Yellow-colored peptides containing a prosthetic group were composed of two polypeptide chains and the prosthetic group was covalently bound to two residues at positions 55 and 106, which could not be identified yet. The molecular weight of the subunit was 13,500 excluding the binding residues and the prosthetic group. Various structural features are discussed.