Isolation and properties of an S-adenosyl-L-methionine binding protein from the green alga, Chlamydomonas reinhardi

A protein that binds S-adenosyl-L-methionine (AdoMet) was isolated by successive chromatography from vegetative cells of Chlamydomonas reinhardi. The relative molecular masses of native and denatured proteins were calculated to be 15 kDa and 16 kDa, respectively. The reaction was specific to AdoMet and reversible as shown by competition experiments. The optimal pH for binding ranged between 7.5 and 9.0, and the apparent Ka for AdoMet was 1.0 μmol/L. Results suggested that the protein may function as the carrier to stabilize AdoMet, which is otherwise labile in the cellular environment.