CLONING, CHARACTERIZATION AND FUNCTIONAL-ANALYSIS OF GROESL OPERON FROM THERMOPHILIC CYANOBACTERIUM SYNECHOCOCCUS-VULCANUS

Genes encoding 10914Da and 58267Da polypeptides homologous to groES an d groEL of Escherichia coli were cloned and sequenced from a thermophi lic cyanobacterium, Synechococcus vulcanus. The deduced amino acid seq uence of the GroEL protein was much more homologous to GroELs of other cyanobacteria which accompany GroES than another GroEL homolog of S. vulcanus (GroEL2) reported previously (M. Furuki, N. Tanaka, T. Hiyama , and H. Nakamoto, Biochim. Biophys. Acta 1294 (1996) 106-110). We des ignate the gene as groEL1 to distinguish it from the non-operon formin g groEL2 gene. A 9-base pair inverted repeat sequence (TTAGCACTC-N-9-G AGTGCTAA) was located upstream of the promoter region of groEL1, which was absent in groEL2. Southern blot analysis indicated that only one groESL1 operon was present in the genomic DNA of S. vulcanus. The amou nt of the bicistronic, 2.3 kb transcript of groESL1 operon increased 3 0-fold within 30 min upon heat shock. The increase was completely inhi bited by chloramphenicol, suggesting the involvement of heat-induced p roduction of a polypeptide. Introduction of the cloned groEL2 gene int o a groEL defective mutant of E. coli resulted in the complementation of heat sensitivity, which contrasted with the previous result with gr oEL2. (C) 1997 Elsevier Science B.V.