BRASSICA-NAPUS PLASTID AND MITOCHONDRIAL CHAPERONIN-60 PROTEINS CONTAIN MULTIPLE DISTINCT POLYPEPTIDES

Plastid chaperonin-60 protein was purified to apparent homogeneity from Brassica napus using a novel protocol. The purified protein, which migrated as a single species by nondenaturing polyacrylamide gel electrophoresis, contained four polypeptides: three variants of p60(cpn60 alpha) p60(cpn60 beta). Partial amino acid sequence determination demonstrated that each variant of p60(cpn60 alpha) is a distinct translation product. During this study, additional chaperonin-60 proteins were purified. These proteins, which were free from contaminating plastid chaperonin-60, were separated into at least two high molecular weight species that were resolved only by nondenaturing polyacrylamide gel electrophoresis. These proteins contained three 60-kD polypeptides. Two of these polypeptides were recognized by existing antisera, whereas the third was not. Partial amino acid sequence data revealed that each of these, including the immunologically distinct polypeptide, is a chaperonin-60 subunit of putative mitochondrial origin. The behavior or chaperonin-60 proteins during blue A Dyematrex chromatography suggests that this matrix may be generally useful for the identification of chaperonin-60 proteins.