In Silico Structural and Functional Characterization of HtrA Proteins of Leptospira spp.: Possible Implications in Pathogenesis.

Leptospirosis is a zoonosis caused by the pathogenic bacteria of the genus Leptospira. The identification of conserved outer membrane proteins among pathogenic strains is a major research target in elucidating mechanisms of pathogenicity. Surface-exposed proteins are most probably the ones involved in the interaction of leptospires with the environment. Some spirochetes use outer membrane proteases as a way to penetrate host tissues. HtrA is a family of proteins found in various cell types, from prokaryotes to primates. They are a set of proteases usually composed of a serine protease and PDZ domains, and they are generally transported to the periplasm. Here, we identified four genes-annotated as HtrA, LIC11111, LIC20143, LIC20144 and LIC11037-and another one annotated as a serine protease, LIC11112. It is believed that the last forms a functional heterodimer with LIC11111, since they are organized in one operon. Our analyses showed that these proteins are highly conserved among pathogenic strains. LIC11112, LIC20143, and LIC11037 have the serine protease domain with the conserved catalytic triad His-Asp-Ser. This is the first bioinformatics analysis of HtrA proteins from Leptospira that suggests their proteolytic activity potential. Experimental studies are warranted to elucidate this possibility.