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Open Access Highly Accessed Research article

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

Outi Heikkinen1, Raili Seppala2, Helena Tossavainen2, Sami Heikkinen1, Harri Koskela3, Perttu Permi2* and Ilkka Kilpeläinen1*

Author Affiliations

1 Laboratory of Organic Chemistry, Department of Chemistry, P.O. Box 55, FI-00014 University of Helsinki, Finland

2 Program in Structural Biology and Biophysics, Institute of Biotechnology, P.O. Box 65, FI-00014 University of Helsinki, Finland

3 Finnish Institute for Verification of the Chemical Weapons Convention, P.O. Box 55, FI-00014 University of Helsinki, Finland

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BMC Structural Biology 2009, 9:17  doi:10.1186/1472-6807-9-17

Published: 24 March 2009

Abstract

Background

Staphylococcus aureus is a Gram-positive pathogenic bacterium causing many kinds of infections from mild respiratory tract infections to life-threatening states as sepsis. Recent emergence of S. aureus strains resistant to numerous antibiotics has created a need for new antimicrobial agents and novel drug targets. S. aureus PrsA is a membrane associated extra-cytoplasmic lipoprotein which contains a parvulin-type peptidyl-prolyl cis-trans isomerase domain. PrsA is known to act as an essential folding factor for secreted proteins in Gram-positive bacteria and thus it is a potential target for antimicrobial drugs against S. aureus.

Results

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.

Conclusion

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.