Covalent modification of ribulose 1,5-bisphosphate carboxylase/oxygenase in Rhodomicrobium vannielii

The most abundant phosphorus-containing polypeptide in the purple non-sulphur bacterium Rhodomic-robium vannielii has been identified by a combination of immunoprecipitation and sucrose density gradient centrifugation as the large subunit of ribulose 1,5-bisphosphate carboxylase/oxygenase. The covalent modification of the large subunit involves the phosphorylation of one or more tyrosine residues and appears to occur prior to assembly of the large subunit into the mature enzyme. In addition, the phosphorylated form of the large subunit was found to exist in at least two distinct protein complexes of Mr 410,000 and 440,000.