The crystal structure of the leptospiral hypothetical protein LIC12922 reveals homology with the periplasmic chaperone SurA

ABSTRACT

Leptospirosis is a world spread zoonosis caused by members of the genus Leptospira. Although leptospireswere identified as the causal agent of leptospirosis almost 100 years ago, little is known about their biology,which hinders the development of new treatment and prevention strategies. One of the severalaspects of the leptospiral biology not yet elucidated is the process by which outer membrane proteins (OMPs) traverse the periplasm and are inserted into the outer membrane. The crystal structure determination of the conserved hypothetical protein LIC12922 from Leptospira interrogans revealed a two domain protein homologous to the Escherichia coli periplasmic chaperone SurA. The LIC12922 NC-domain isstructurally related to the chaperone modules of E. coli SurA and trigger factor, whereas the parvulindomain is devoid of peptidyl prolyl cis–trans isomerase activity. Phylogenetic analyses suggest a relationshipbetween LIC12922 and the chaperones PrsA, PpiD and SurA. Based on our structural and evolutionaryanalyses, we postulate that LIC12922 is a periplasmic chaperone involved in OMPs biogenesis inLeptospira spp. Since LIC12922 homologs were identified in all spirochetal genomes sequenced to date,this assumption may have implications for the OMPs biogenesis studies not only in leptospires but in the entire Phylum Spirochaetes.