Calander Home 2001-2002 2002-2003 February 4 - Prof. Kara L. Bren Dynamics of Thermophilic and Mesophilic Cytochromes c: How are Flexibility and Stability Related? Date: 2/4/02 Time: Noon to 1PM Place: BSBE 6-101 Prof. Kara L. Bren - Dept. of Chemistry, University of Rochester will present: Dynamics of Thermophilic and Mesophilic Cytochromes c: How are Flexibility and Stability Related? Part 1: Mitochondiral ferricytochromes c undergo exchange of an axial heme ligand (Met80) for one or more non-native ligands under denaturing or partially denaturing conditions. We have employed 1H NMR spectroscopy to detect and analyze non-native conformations of paramagnetic ferricytochromes c (cyt c) populated in urea or guanidinum chloride. Properties of unfolding intermediates and of residual structure in the denatured state will be discussed, as will the dependence of species observed on denaturant used. Implications for cytochrome c's role in triggering apoptosis will be discussed. Part 2: Stability and conformational entropy of thermophilic and mesophilicproteins Proteins isolated from organisms that thrive at elevated temperatures (thermophiles) are proposed to display enhanced conformational rigidity at room temperature in comparison with homologous proteins from mesophiles (organisms adapted to 20 - 40 degrees C). Enhanced rigidity, however, comes with an entropic cost. To gain a better understanding of the complex relationship between protein stability and flexibility, the temperature dependence of the dynamics of thermophilic and mesophilic cytochromes c has been investigated using molecular NMR spectroscopy. These studies provide residue-specific information on motions that occur over a wide range of time scales (ps - ms). Thermodynamic implications of differences in flexibility observed for the thermophile and mesophile will bepresented. Pizza Lunch will be provided by John Lipscomb. Thanks John.