| Title: | Conformational Entropy from Slowly Relaxing Local Structure Analysis of (15)N-H Relaxation in Proteins: Application to Pheromone Binding to MUP-I in the 283-308 K Temperature Range |
| Address: | "Central European Institute of Technology, Masaryk University , Kamenice 5, 62500 Brno, Czech Republic. National Center for Biomolecular Research, Faculty of Science, Masaryk University , Kamenice 5, 62500 Brno, Czech Republic. The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University , Ramat-Gan 52900, Israel" |
| ISSN/ISBN: | 1520-5207 (Electronic) 1520-5207 (Linking) |
| Abstract: | "The slowly relaxing local structure (SRLS) approach is applied to (15)N-H relaxation from the major urinary protein I (MUP-I), and its complex with pheromone 2-sec-butyl-4,5-dihydrothiazol. The objective is to elucidate dynamics, and binding-induced changes in conformational entropy. Experimental data acquired previously in the 283-308 K temperature range are used. The N-H bond is found to reorient globally with correlation time, tau(1,0), and locally with correlation time, tau(2,0), where tau(1,0) >> tau(2,0). The local motion is restricted by the potential u = -c(0)(2)D(00)(2), where D(00)(2) is the Wigner rotation matrix element for L = 2, K = 0, and c(0)(2) evaluates the strength of the potential. u yields straightforwardly the order parameter, ?Γ+D(00)(2)?Γ?, and the conformational entropy, S(k), both given by P(eq) = exp(-u). The deviation of the local ordering/local diffusion axis from the N-H bond, given by the angle beta, is also determined. We find that c(0)(2) congruent with 18 +/- 4 and tau(2,0) = 0-170 ps for ligand-free MUP-I, whereas c(0)(2) congruent with 15 +/- 4 and tau(2,0) = 20-270 ps for ligand-bound MUP-I. beta is in the 0-10 degrees range. c(0)(2) and tau(2,0) decrease, whereas beta increases, when the temperature is increased from 283 to 308 K. Thus, SRLS provides physically well-defined structure-related (c(0)(2) and ?Γ+D(00)(2)?Γ?), motion-related (tau(2,0)), geometry-related (beta), and binding-related (S(k)) local parameters, and their temperature-dependences. Intriguingly, upon pheromone binding the conformational entropy of MUP-I decreases at high temperature and increases at low temperature. The very same experimental data were analyzed previously with the model-free (MF) method which yielded 'global' (in this context, 'relating to the entire 283-308 K range') amplitude (S(2)) and rate (tau(e)) of the local motion, and a phenomenological exchange term (R(ex)). S(2) is found to decrease (implying implicitly 'global' increase in S(k)) upon pheromone binding" |
| Keywords: | *Entropy Hydrogen/*chemistry Nitrogen Isotopes Protein Conformation Proteins/*chemistry *Temperature; |
| Notes: | "MedlineZidek, Lukas Meirovitch, Eva eng Research Support, Non-U.S. Gov't 2017/08/22 J Phys Chem B. 2017 Sep 21; 121(37):8684-8692. doi: 10.1021/acs.jpcb.7b06049. Epub 2017 Sep 8" |
