DYNAMIC CHARACTERIZATION OF SUBSTRATE RECOGNITION IN RNASE Z

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Enzyme dynamics are being revealed to play an increasingly important role in bimolecular function. While much has been learned about the role motions play in the recognition and release of small substrates, little is understood about the recognition of large substrates and, in particular, the binding of large substrates to large proteins with highly flexible regions. One such system that will provide insight into this poorly understood area is ribonuclease Z (RNase Z). RNase Z is a 65 kD homodimer responsible for the endonucleolytic processing of the 3' end of transfer RNAs. RNase Z is comprised of two domains: a central domain and an arm protrusion. The central domain is homologus to class B ?-lactamases and is responsible for the cleavage reaction. The arm protrusion of approximately 40 amino acids is believed to be essential for substrate recognition. It is hypothesized that dynamics of the arm become dramatically altered upon substrate binding and are responsible for the coordination and activation of the catalytic domain. Solution phase NMR spectroscopy is the ideal technique to study the dynamics of RNase Z as it affords site-specific quantification of thermodynamic parameters. These studies will not only help elucidate the poorly understood mechanism of RNase Z, but also to further understanding of protein motions and their role in biological function.