David Tierney, PhD University of New Mexico dtierney@unm.edu Phone:(505) 277-2505 Personal Website

Title: Structural Studies on the Role of Zinc in Bacterial Proliferation

The most successful antibiotics act as mechanism-based inhibitors of specific cellular processes involved in bacterial proliferation and virulence.  Mechanistic investigations of VanX (vancomycin resistance) and the metallo-b-lactamases (penicillin resistance), which play defensive roles for an individual bacterium, and of the AHL-lactonase, which plays a prominent role in intercellular bacterial communication (quorum quenching), controlling virulence, are proposed.  The common thread to the systems to be studied is their dependence on Zn(II) for activty, and their ability to bind cobalt at the active site as the high-spin (hs) Co(II) ion.  Each represents an important clinical target, and the spectroscopic studies proposed here will aid directly in the development of broadly effective mechanism-based inhibitors of these enzymes.  Structural spectroscopy – including x-ray absorption spectroscopy (XAS), multi-frequency electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR), paramagnetic NMR, and NMR dispersion (NMRD) – of the native Zn and Co-substituted enzymes will be employed to characterize stable resting states and catalytically relevant intermediates.  These studies will aid directly in the development of clinically viable inhibitors.  For each enzyme under study, we plan to first use XAS to ensure transferability of magnetic resonance and optical results obtained from the cobalt enzymes to reactivity of the native zinc enzyme.  Magnetic resonance experiments will probe more subtle structural details, and in conjunction with rapid-freeze-quench (RFQ) techniques, will establish a structural timeline for catalysis.