title: Changes in the 31P NMR spectrum of rabbit muscle myosin subfragment 1. MgADP with temperature.
abstract: In pioneering studies on the 31P NMR spectra of MgADP bound to the "molecular motor" myosin subfragment 1 (S1) in the temperature range of 0 to 25 degrees C, Shriver and Sykes [Biochemistry 20 (1981) 2004-2012/6357-6362; Biochemistry 21 (1982) 3022-3028], proposed that MgADP binds to myosin S1 as a mixture of two interconvertible conformers with different chemical shifts for the beta-P resonance of the S1-bound MgADP and that the concentrations of these conformers are related by an equilibrium constant K(T). Their model implied that the weighted average of the chemical shifts of the beta-P(MgADP) for S1-bound MgADP asymptotically approaches a high temperature limit. Here, and in our earlier paper [K. Konno, K. Ue, M. Khoroshev, H., Martinez, B.D. Ray, M.F. Morales, Proc. Natl. Acad. Sci. USA 97 (2000) 1461-1466], we report experimental similarities to Shriver and Sykes, but diverge from them (especially at 0 degrees C) in not finding two distinct peaks and in finding that the average chemical shift does not change with temperature. Our observations can be explained by chemical exchange of beta-P(MgADP) of S1-bound MgADP between two nearly energetically equivalent environments.
authors.affiliation: Department of Physics, Indiana University-Purdue University at Indianapolis (IUPUI) Indianapolis, IN 46202, USA. bray@iupui.edu
authors.forename: Bruce D
authors.initials: BD
authors.lastname: Ray
authors.forename: Mikhail I
authors.initials: MI
authors.lastname: Khoroshev
authors.forename: Kathleen
authors.initials: K
authors.lastname: Ue
authors.forename: Manuel F
authors.initials: MF
authors.lastname: Morales
authors.forename: B D
authors.initials: BD
authors.lastname: Nageswara Rao
mesh_terms: D000244:Adenosine Diphosphate / Q000737:chemistry*; D000818:Animals; D008274:Magnesium; D009682:Magnetic Resonance Spectroscopy; D015879:Myosin Subfragments / Q000737:chemistry*; D011817:Rabbits; D013696:Temperature
chemical_list: D015879:Myosin Subfragments; D000244:Adenosine Diphosphate; D008274:Magnesium