title: Backbone dynamics of the ribonuclease binase active site area using multinuclear ((15)N and (13)CO) NMR relaxation and computational molecular dynamics.
abstract: The nano-pico second backbone dynamics of the ribonuclease binase, homologous to barnase, is investigated with (15)N, (13)C NMR relaxation at 11.74 and 18.78 T and with a 1.1 ns molecular dynamics simulation. The data are compared with the temperature factors reported for the X-ray structure of this enzyme. The molecular dynamics and X-ray data correspond well and predict motions in the loops 56-61 and 99-104 that contain residues that specifically recognize substrate and are catalytic (His101), respectively. In contrast, the (15)N relaxation data indicate that these loops are mostly ordered at the nano-pico second time scale. Nano-pico second motions in the recognition loop 56-61 are evident from (13)CO-(13)C cross relaxation data, but the mobility of the catalytic loop 99-104 is not detected by (13)CO cross relaxation either. From the results of this and previous work [Wang, L., Pang, Y., Holder, T., Brender, J. R., Kurochkin, A., and Zuiderweg, E. R. P. (2001) Proc. Natl. Acad. Sci. U.S.A., 98, 7684-7689], the following dynamical characterization of the active site area of binase emerges: a beta sheet, rigid at all probed time scales, supports the catalytic residue Glu 72. Both substrate-encapsulating loops are mobile on both fast and slow time scales, but the fast motions of the loop which contains the other catalytic residue, His 101, as predicted by B-factors and computational molecular dynamics is not detected by NMR relaxation. This work strongly argues for the use of several measures in the study of protein dynamics.
authors.affiliation: Department of Biological Chemistry, University of Michigan, Biophysics Research Division, Ann Arbor, Michigan 48109-1055, USA.
authors.forename: Yuxi
authors.initials: Y
authors.lastname: Pang
authors.forename: Matthias
authors.initials: M
authors.lastname: Buck
authors.forename: Erik R P
authors.initials: ER
authors.lastname: Zuiderweg
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002247:Carbon Isotopes; D002248:Carbon Monoxide / Q000737:chemistry; D004722:Endoribonucleases / Q000737:chemistry*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009587:Nitrogen Isotopes; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D011487:Protein Conformation
chemical_list: D002247:Carbon Isotopes; D009587:Nitrogen Isotopes; D002248:Carbon Monoxide; D004722:Endoribonucleases; C022543:ribonuclease T(2)