title: Propagation of dynamic changes in barnase upon binding of barstar: an NMR and computational study.
abstract: NMR spectroscopy and computer simulations were used to examine changes in chemical shifts and in dynamics of the ribonuclease barnase that result upon binding to its natural inhibitor barstar. Although the spatial structures of free and bound barnase are very similar, binding results in changes of the dynamics of both fast side-chains, as revealed by (2)H relaxation measurements, and NMR chemical shifts in an extended beta-sheet that is located far from the binding interface. Both side-chain dynamics and chemical shifts are sensitive to variations in the ensemble populations of the inter-converting molecular states, which can escape direct structural observation. Molecular dynamics simulations of free barnase and barnase in complex with barstar, as well as a normal mode analysis of barnase using a Gaussian network model, reveal relatively rigid domains that are separated by the extended beta-sheet mentioned above. The observed changes in NMR parameters upon ligation can thus be rationalized in terms of changes in inter-domain dynamics and in populations of exchanging states, without measurable structural changes. This provides an alternative model for the propagation of a molecular response to ligand binding across a protein that is based exclusively on changes in dynamics.
authors.affiliation: Swedish NMR Centre at Göteborg University, Box 465, 405 30 Göteborg, Sweden.
authors.forename: Anastasia
authors.initials: A
authors.lastname: Zhuravleva
authors.forename: Dmitry M
authors.initials: DM
authors.lastname: Korzhnev
authors.forename: Svetlana B
authors.initials: SB
authors.lastname: Nolde
authors.forename: Lewis E
authors.initials: LE
authors.lastname: Kay
authors.forename: Alexander S
authors.initials: AS
authors.lastname: Arseniev
authors.forename: Martin
authors.initials: M
authors.lastname: Billeter
authors.forename: Vladislav Yu
authors.initials: VY
authors.lastname: Orekhov
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D003198:Computer Simulation; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D012260:Ribonucleases / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; C057438:barstar protein, Bacillus amyloliquefaciens; D012260:Ribonucleases; C019760:Bacillus amyloliquefaciens ribonuclease