Domain orientation in β-cyclodextrin-loaded maltose binding protein: Diffusion anisotropy measurements confirm the results of a dipolar coupling study

Maltose binding protein (MBP) is a 370-residue two-domain molecule involved in bacterial chemotaxis and sugar uptake. Rotational diffusion tensors were calculated for a complex between MBP and β-cyclodextrin using backbone 15N T1 and T1ρ relaxation times and steady state 1H-15N NOE values. The tensors obtained for each of the two domains in the protein were subsequently used to determine the relative domain orientation in the molecule. The average domain orientation determined using this approach agrees well with results from dipolar coupling data, but differs significantly from the domain orientation deduced from X-ray studies of the complex