Ac. Drohat et al., The use of dipolar couplings for determining the solution structure of ratapo-S100B(beta beta), PROTEIN SCI, 8(4), 1999, pp. 800-809
The relative orientations of adjacent structural elements without many well
-defined NOE contacts between them are typically poorly defined in NMR stru
ctures. For apo-S100B(PP) and the structurally homologous protein calcyclin
, the solution structures determined by conventional NMR exhibited consider
able differences and made it impossible to draw unambiguous conclusions reg
arding the Ca2+-induced conformational change required for target protein b
inding. The structure of rat apo-S100B(PP) was recalculated using a large n
umber 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 uncertain
ty in NOE-based structures. The structure of apo-S100B(PP) indicates a mini
mal change in the first, pseudo-EF-hand Ca2+ binding site, but a large reor
ientation of helix 3 in the second, classical EF-hand upon Ca2+ binding.