Homomultimeric protease in the hyperthermophilic bacterium Thermotoga maritima has structural and amino acid sequence homology to bacteriocins in mesophilic bacteria

A novel homomultimeric protease (>669 kDa), based on 31 kDa subunits, was p urified from cell extracts of the hyperthermophilic bacterium Thermotoga ma ritima, This protease exhibits activity toward chymotrypsin and trypsin sub strates, optimally at 90 degrees C and pH 7.1, and has a half-life of 36 mi n at 95 degrees C, Transmission electron microscopy established that the pr otease consists of a large globular assembly which appears circular from th e front view. The function of this protease in T. maritima remains unclear, although putative homologs include a 29 kDa antigen from Mycobacterium tub erculosis and a 31 kDa monomer of a high molecular weight bacteriocin produ ced by Brevibacterium linens [Valdes-Stauber, N. and Scherer, S. (1996) App l, Environ, Microbiol, 62, 1283-1286], The relationship of these mesophilic proteins to the T, maritima protease suggests that their antibacterial act ivity may involve elements of proteolysis, and raises the prospect for anti microbial ecological strategies in hyperthermophilic niches. (C) 1998 Feder ation of European Biochemical Societies.