The nature of L8 and L8S8 forms of ribulose bisphosphate carboxylase/oxygenase from Chromatium vinosum.

L8 and L8S8 forms of ribulose bisphosphate carboxylase/oxygenase (RubisCO) have been prepared from Chromatium vinosum by the extremely mild method of centrifugal fractionation. Only the L8S8 form is detectable in crude extracts of this organism. Both forms show immunological identify in double diffusion studies using antibody to L subunits of the L8S8 form. L subunits from both L8 and L8S8 enzymes are identical by the criteria of peptides observed after limited proteolysis and N-terminal sequence analysis. In addition, these subunits show regions of homology with L subunits from Rhodospirillum rubrum, Anacystis nidulans, and spinach. S subunits of the C. vinosum enzyme are completely homologous to those from A. nidulans and higher plants from the 18th through 25th residue, a stretch preceded in all cases by two basic amino acids.