Complete primary structure of ribulosebisphosphate carboxylase/oxygenase from Rhodospirillum rubrum.

Of the 14 cyanogen bromide fragments derived from Rhodospirillum rubrum ribulosebisphosphate carboxylase/oxygenase, four are too large to permit complete sequencing by direct means [F. C. Hartman, C. D. Stringer, J. Omnaas, M. I. Donnelly, and B. Fraij (1982) Arch. Biochem. Biophys. 219, 422-437]. These have now been digested with proteases, and the resultant peptides have been purified and sequenced, thereby providing the complete sequences of the original fragments. With the determination of these sequences, the total primary structure of the enzyme is provided. The polypeptide chain consists of 466 residues, 144 (31%) of which are identical to those at corresponding positions of the large subunit of spinach ribulosebisphosphate carboxylase/oxygenase. Despite the low overall homology, striking homology between the two species of enzyme is observed in those regions previously implicated at the catalytic and activator sites.