1H and 15N NMR assignment and solution structure of the SH3 domain of spectrin: Comparison of unrefined and refined structure sets with the crystal structure

The assignment of the ¹H and ¹⁵Nnuclear magnetic resonance spectra of the Src-homology region 3 domain ofchicken brain -spectrin has been obtained. A set of solutionstructures has been determined from distance and dihedral angle restraints,which provide a reasonable representation of the protein structure insolution, as evaluated by a principal component analysis of the globalpairwise root-mean-square deviation (rmsd) in a large set of structuresconsisting of the refined and unrefined solution structures and the crystalstructure. The solution structure is well defined, with a lower degree ofconvergence between the structures in the loop regions than in the secondarystructure elements. The average pairwise rmsd between the 15 refinedsolution structures is 0.71 ± 0.13 Å for the backbone atoms and1.43 ± 0.14 Å for all heavy atoms. The solution structure isbasically the same as the crystal structure. The average rmsd between the 15refined solution structures and the crystal structure is 0.76 Å forthe backbone atoms and 1.45 ± 0.09 Å for all heavy atoms. Thereare, however, small differences probably caused by intermolecular contactsin the crystal structure.