A stress protein is induced in the deep-sea barophilic hyperthermophile Thermococcus barophilus when grown under atmospheric pressure

The whole-cell protein inventory of the deep-sea barophilic hyperthermophil e Thermococcus barophilus was examined by one-dimensional SDS gradient gel electrophoresis when grown under different pressure conditions at 85 degree s C (T-opt). One protein (P60) with a molecular mass of approximately 60 kD a was prominent at low pressures (0.3 MPa hydrostatic pressure and 0.1 MPa atmospheric pressure) but not at deep-sea pressures (10, 30, and 40 MPa). A bout 17 amino acids were sequenced from the N-terminal end of the protein. Sequence homology analysis in the GenBank database showed that P60 most clo sely resembled heat-shock proteins in some sulfur-metabolizing Archaea. A h igh degree of amino acid identity (81%-93%) to thermosome subunits in Therm ococcales strains was found. Another protein (P35) with molecular mass of a pproximately 35.5 kDa was induced at 40 MPa hydrostatic pressure but not un der low-pressure conditions. No amino acid sequence homology was found for this protein when the 40 amino acids from the N-terminal end were compared with homologous regions of proteins from databases. A PTk diagram was gener ated for T. barophilus. The results suggest that P-habitat is about 35 MPa, which corresponds to the in situ pressure where the strain was obtained.