Immunophilins are a superfamily of highly conserved proteins, of which many exhibit peptidyl-prolyl cis-trans isomerase (PPIase) or rotamase activity. They catalyse the rate limiting step of protein folding, the isoform change of proline residues from cis to trans orientation. There are three families of immunophilins which are classified by their respective immunosuppressant binding partners. Cyclophilins (Cyp) are bound by Cyclosporin A, FK506-binding proteins (FKBPs) bind FK506 and rapamycin, and parvulins bind juglone. Cyclophilins have been identified in nearly all living organisms and are associated with bacterial virulence. Due to the highly conserved nature of cyclophilins, they present as novel anti-virulence targets for many pathogenic, antibiotic-resistant bacteria, such as Burkholderia pseudomallei, which encodes for two Cyclophilin genes, ppiA and ppiB.
B. pseudomallei is the causative agent of melioidosis, which is endemic in South-East Asia and Northern Australia. Even with appropriate antibiotic treatment the mortality rate of melioidosis in Australia is still 20%. Medical countermeasures are urgently needed to decrease the occurrence and severity of these infections.
This project aims to characterize the two Cyclophilins found in B. pseudomallei and determine if these proteins play a role in the virulence of B. pseudomallei infections. Three unmarked knockout mutants will be created, Bps∆ppiA, Bps∆ppiB and Bps∆ppiA∆ppiB. Here we present the preliminary in vitro phenotypes of these mutant strains. B. pseudomallei ppiA and ppiB were overexpressed and purified, and their PPIase activity determined.