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The use of dipolar couplings for determining the solution structure of rat apo-S100B(ββ)

Published online by Cambridge University Press:  01 April 1999

ALEXANDER C. DROHAT
Affiliation:
Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, 108 North Greene Street, Baltimore, Maryland 21201
NICO TJANDRA
Affiliation:
Laboratory of Biophysical Chemistry, Building 3, Room 418, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892-0380
DONNA M. BALDISSERI
Affiliation:
Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, 108 North Greene Street, Baltimore, Maryland 21201
DAVID J. WEBER
Affiliation:
Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, 108 North Greene Street, Baltimore, Maryland 21201
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Abstract

The relative orientations of adjacent structural elements without many well-defined NOE contacts between them are typically poorly defined in NMR structures. For apo-S100B(ββ) and the structurally homologous protein calcyclin, the solution structures determined by conventional NMR exhibited considerable differences and made it impossible to draw unambiguous conclusions regarding the Ca2+-induced conformational change required for target protein binding. The structure of rat apo-S100B(ββ) was recalculated using a large number of constraints derived from dipolar couplings that were measured in a dilute liquid crystalline phase. The dipolar couplings orient bond vectors relative to a single-axis system, and thereby remove much of the uncertainty in NOE-based structures. The structure of apo-S100B(ββ) indicates a minimal change in the first, pseudo-EF-hand Ca2+ binding site, but a large reorientation of helix 3 in the second, classical EF-hand upon Ca2+ binding.

Type
Research Article
Copyright
© 1999 The Protein Society

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