Solution structure of the parvulin-type PPIase domain of Staphylococcus aureus PrsA – Implications for the catalytic mechanism of parvulins

We have solved a high-resolution solution structure of the parvulin-type peptidyl-prolyl cis-trans isomerase domain of S. aureus PrsA (PrsA-PPIase). The results of substrate peptide titrations pinpoint the active site and demonstrate the substrate preference of the enzyme. With detailed NMR spectroscopic investigation of the orientation and tautomeric state of the active site histidines we are able to give further insight into the structure of the catalytic site. NMR relaxation analysis gives information on the dynamic behaviour of PrsA-PPIase.Detailed structural description of the S. aureus PrsA-PPIase lays the foundation for structure-based design of enzyme inhibitors. The structure resembles hPin1-type parvulins both structurally and regarding substrate preference. Even though a wealth of structural data is available on parvulins, the catalytic mechanism has yet to be resolved. The structure of S. aureus PrsA-PPIase and our findings on the role of the conserved active site histidines help in designing further experiments to solve the detailed catalytic mechanism.Staphylococcus aureus is a Gram-positive bacterium causing many kinds of infections from mild respiratory tract infections to life-threatening states as sepsis. It produces many toxins and has a remarkable ability to acquire resistance to antimicrobial drugs. Many S. aureus strains have acquired resistance to commonly used antibiotics and some strains are becoming multi-resistant. Methicillin-resistant strain of Staphylococcus aureus (MRSA) is the principal cause of severe nosocomial infections which can be fatal to compromised patients. Whole genome sequencing of two MRSA strains in 2001 was regarded as a way to find targets for novel antibiotics against infections caused by MRSA [1].PrsA protein is found ubiquitously in Gram-positive bacteria, including S. aureus [Swiss-Prot:P60747], but not in Gram-negative ones [2,3]. By sequence homology PrsA contains a parvulin-type peptidyl-prolyl cis-trans isomera