Long-Range Effect of Mutation of Calcium Binding Asparates on the Catalytic Activity of Alkaline Protease from Pseudomonas aeruginosa

Abstract

Apart from a catalytic domain, the alkaline protease of Pseudomonas aeruginosa has a novel parallel beta-helix domain stabilized through Ca2+ binding. In order to clarify the importance of the beta-helix structure in maturation of the enzyme, aspartic residue D-356 or D-365 in the Ca2+ binding sequence motif was replaced with L-alanine, and the catalytic activity of each mutant was assayed. These mutants did not show any proteolytic activity, although the composition of their polypeptide chains was the same as that of the wild type except for the mutated alanine residue. These results suggest that D-356 and D-365 are important in control of the beta-helix folding induced by Ca2+ binding and that incomplete beta-helix folding due to the lack of their side-chains affects the maturation of the enzyme in the long-range order.