Abstract:

The psychrotropic bacterium, Pseudoalteromonas sp. QI-1, which produces extracellular cold-active protease, was isolated from Antarctic seawater. The genomic DNA of this bacterium was used to construct a plasmid genomic library with the goal of screening cold-active protease genes. Gene pro-2127 with an open reading frame of 2127 bp encoding protease PRO-2127 was cloned and sequenced. Alignment of amino acid sequences suggested that the precursor of PRO-2127 was a member of subfamily S8A, and that it might contain four domains: a signal peptide, an N-terminal prosequence, a catalytic domain and a C-terminal extension. Amino acids Asp185, His244 and Ser425 might form a catalytic triad. PRO-2127 showed some structural features common to psychrophilic enzymes, such as a decrease in Arg residues and the Arg/(Arg+Lys) ratio. Heterologous expression of pro-2127 in Escherichia coli BL21 (DE3) by pColdIII was also successfully observed in this study.

Key words: Antarctic, Pseudoalteromonas, cold-active protease, gene cloning and expression