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

Plastid chaperonin-60 protein was purified to apparent homogeneity fro m Brassica napus using a novel protocol. The purified protein, which m igrated as a single species by nondenaturing polyacrylamide gel electr ophoresis, contained four polypeptides: three variants of p60(cpn60 al pha) p60(cpn60 beta). Partial amino acid sequence determination demons trated that each variant of p60(cpn60 alpha) is a distinct translation product. During this study, additional chaperonin-60 proteins were pu rified. These proteins, which were free from contaminating plastid cha peronin-60, were separated into at least two high molecular weight spe cies that were resolved only by nondenaturing polyacrylamide gel elect rophoresis. These proteins contained three 60-kD polypeptides. Two of these polypeptides were recognized by existing antisera, whereas the t hird was not. Partial amino acid sequence data revealed that each of t hese, including the immunologically distinct polypeptide, is a chapero nin-60 subunit of putative mitochondrial origin. The behavior or chape ronin-60 proteins during blue A Dyematrex chromatography suggests that this matrix may be generally useful for the identification of chapero nin-60 proteins.