CHARACTERIZATION AND SEQUENCE COMPARISON OF TEMPERATURE-REGULATED CHAPERONINS FROM THE HYPERTHERMOPHILIC ARCHAEON ARCHAEOGLOBUS-FULGIDUS

We have cloned and sequenced the genes encoding two chaperonin subunit s (Cpn-alpha and Cpn-beta), from Archaeoglobus fulgidus, a sulfate-red ucing hyperthermophilic archaeon. The genes encode proteins of 545 ami no acids with calculated M-r of 58 977 and 59 683. Both proteins have been identified in cytoplasmic fractions of A. fulgidus by Western ana lysis using antibodies raised against one of the subunits expressed in Escherichia coli, and by N-terminal amino acid sequencing of chaperon in complexes purified by immunoprecipitation. The chaperonin genes app ear to be under heat shock regulation, as both proteins accumulate fol lowing temperature shift-up of growing A. fulgidus cells, implying a r ole of the chaperonin in thermoadaptation. Canonical Box A and Box B a rchaeal promoter sequences, as well as additional conserved putative s ignal sequences, are located upstream of the start codons. A phylogene tic analysis using all the available archaeal chaperonin sequences, su ggests that the cc and B subunits are the results of late gene duplica tions that took place well after the establishment of the main archaea l evolutionary lines. (C) 1998 Elsevier Science B.V. All rights reserv ed.