Backbone dynamics of the calcium-signaling protein apo-S100B as determined by 15N NMR relaxation.

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TitleBackbone dynamics of the calcium-signaling protein apo-S100B as determined by 15N NMR relaxation.
Publication TypeJournal Article
Year of Publication2001
AuthorsInman, KG, Baldisseri, DM, Miller, KE, Weber, DJ
JournalBiochemistry
Volume40
Issue12
Pagination3439-48
Date Published2001 Mar 27
ISSN0006-2960
KeywordsAmino Acid Sequence, Apoproteins, Calcium Signaling, Calcium-Binding Proteins, Computer Simulation, EF Hand Motifs, Models, Molecular, Molecular Sequence Data, Nerve Growth Factors, Nitrogen Isotopes, Nuclear Magnetic Resonance, Biomolecular, Protein Conformation, S100 Proteins, Thermodynamics
Abstract

Backbone dynamics of homodimeric apo-S100B were studied by (15)N nuclear magnetic resonance relaxation at 9.4 and 14.1 T. Longitudinal relaxation (T(1)), transverse relaxation (T(2)), and the (15)N-[(1)H] NOE were measured for 80 of 91 backbone amide groups. Internal motional parameters were determined from the relaxation data using the model-free formalism while accounting for diffusion anisotropy. Rotational diffusion of the symmetric homodimer has moderate but statistically significant prolate axial anisotropy (D( parallel)/D( perpendicular) = 1.15 +/- 0.02), a global correlation time of tau(m) = 7.80 +/- 0.03 ns, and a unique axis in the plane normal to the molecular symmetry axis. Of 29 residues at the dimer interface (helices 1 and 4), only one has measurable internal motion (Q71), and the order parameters of the remaining 28 were the highest in the protein (S(2) = 0.80 to 0.91). Order parameters in the typical EF hand calcium-binding loop (S(2) = 0.73 to 0.87) were slightly lower than in the pseudo-EF hand (S(2) = 0.75 to 0.89), and effective internal correlation times, tau(e), distinct from global tumbling, were detected in the calcium-binding loops. Helix 3, which undergoes a large, calcium-induced conformational change necessary for target-protein binding, does not show evidence of interchanging between the apo and Ca(2+)-bound orientations in the absence of calcium but has rapid motion in several residues throughout the helix (S(2) = 0.78 to 0.88; 10 < or = tau(e) < or = 30 ps). The lowest order parameters were found in the C-terminal tail (S(2) = 0.62 to 0.83). Large values for chemical exchange also occur in this loop and in regions nearby in space to the highly mobile C-terminal loop, consistent with exchange broadening effects observed.

Alternate JournalBiochemistry
PubMed ID11297409
Grant ListGM58888 / GM / NIGMS NIH HHS / United States
P41 RR-01081 / RR / NCRR NIH HHS / United States