Cloning and heterologous expression of pro-2127,a gene encoding cold-active protease from Pseudoalteromonas sp.QI-1

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.