Analysis of carboxy terminal domain of metalloprotease of elastolytic Aeromonas hydrophila.

We examined the ability of Aeromonas hydrophila to lyse elastin. Eight of 13 strains showed elastolytic activity on agar medium containing elastin and 5 strains did not. In order to examine the involvement of the metalloprotease of A. hydrophila (AMP) in elastolytic activity, we made the amp-deletion mutant strain from an elastolytic strain. The elastolytic activity of the strain decreased with this deletion. The analysis of AMP released into the culture supernatant showed that AMP appeared outside of the cell as the intermediate consisting of a mature domain and carboxy terminal (C-terminal) propeptide domain. Further analysis showed that the intermediate has the ability to lyse elastin and that loss of the C-terminal domain causes loss of the elastolytic activity of the intermediate. We then determined the nucleotide sequence of the amps of all strains used in this study. Phylogenetic analysis revealed that these AMPs were divided into three groups. The AMPs from elastolytic strains belong to group I or group II, and AMPs from non-elastolytic strains belong to group III. The distance between group I and group II is small, but group III is located separately from groups I and II. Comparison of the amino acid residues of the C-terminal domain revealed that there are 13 amino acid residues specific to the C-terminal domain of group III. This indicates that the conformation of the C-terminal propeptide domain formed by these specific amino acid residues is important for AMP to express elastolytic activity.

The carboxy-terminal tail of Aeromonas sobria Serine Protease is associated with the chaperone.

ASP is the only bacterial protease in the kexin group of the subtilisin family. Previous studies have revealed that the ORF2 protein encoded at the 3' end of the asp operon is required for ASP to change from a nascent form into an active form in the periplasm. However, the mechanism by which ORF2 makes contact and interacts with ASP in the maturation process remains unknown. The present study examined the effect of mutations in the carboxy-terminal region of ASP on the ASP maturation process. Both deletion-mutation and amino acid-substitution studies have demonstrated that the histidine residue at position 595 (His-595), the sixth residue from the carboxyl terminus of ASP, is highly involved in the generation of active ASP molecules. An analysis by pull-down assay revealed that mutation at His-595 reduces the efficacy of nascent ASP to transition into active ASP by reducing the ability of ASP to make contact and interact with ORF2. Thus, it appears likely that nascent ASP in the periplasm interacts with ORF2 via the carboxy-terminal region, and His-595 of ASP appears to be an indispensable residue in this interaction.