Chloroplast-encoded protein as a subunit of acetyl-CoA carboxylase in pea plant

The gene product of an open reading frame of the chloroplast genome, accD, that has sequence similarity with a subunit of acetyl-CoA carboxylase from Escherichia coli was detected immunochemically in pea chloroplasts. The apparent molecular mass of the accD protein was 87 kDa on SDS-polyacrylamide gel electrophoresis. The protein was acidic and had less mobility than the calculated value, 67,116. Acetyl-CoA carboxylase activity solubilized from pea chloroplasts was inhibited by antibodies against recombinant accD protein. The antibodies precipitated a polypeptide of 35 kDa containing biotin and a polypeptide of 91 kDa together with the 87-kDa-accD protein. The accD protein formed a complex with the molecular mass of about 700 kDa, probably with the 35- and 91-kDa proteins. These results indicate that the chloroplast-encoded polypeptide, accD protein, is a component of a functional acetyl-CoA carboxylase in chloroplasts and this enzyme is a multi-subunit complex, like that from E. coli. The synthesis of accD protein was not induced by light.