ISOLATION AND CHARACTERIZATION OF A CDNA-ENCODING MITOCHONDRIAL CHAPERONIN-10 FROM ARABIDOPSIS-THALIANA BY FUNCTIONAL COMPLEMENTATION OF ANESCHERICHIA-COLI GROES MUTANT

Chaperonin (Cpn) is one of the molecular chaperones. Cpn10 is a co-fac tor of Cpn60, which regulates Cpn60-mediated protein folding. It is kn own that Cpn10 is located in mitochondria and chloroplasts in plant ce lls. The Escherichia coil homologue of Cpn10 is called GroES. A cDNA f or the Cpn10 homologue was isolated from Arabidopsis thaliana by funct ional complementation of the E. coil groES mutant. The cDNA was 647 bp long and encoded a polypeptide of 98 amino acids. The deduced amino a cid sequence showed approximately 50% identity to mammalian mitochondr ial Cpn10s and 30% identity to GroES. A Northern blot analysis reveale d that the mRNA for the Cpn10 homologue was expressed uniformly in var ious organs and was markedly induced by heat-shock treatment. The Cpn1 0 homologue was constitutively expressed in transgenic tobaccos. Immun ogold and immunoblot analyses following the subcellular fractionation of leaves from transgenic tobaccos revealed that the Cpn10 homologue w as localized in mitochondria and accumulated at a high level in transg enic tobaccos.