Measurement of conformational constraints in an elastin-mimetic protein by residue-pair selected solid-state NMR.

We introduce a solid-state NMR technique for selective detection of a residue pair in multiply labeled proteins to obtain site-specific structural constraints. The method exploits the frequency-offset dependence of cross polarization to achieve 13COi-->15Ni-->13Calphai transfer between two residues. A 13C, 15N-labeled elastin mimetic protein (VPGVG)n, is used to demonstrate the method. The technique selected the Gly3 Calpha signal while suppressing the Gly5 Calpha signal, and allowed the measurement of the Gly3 Calpha chemical shift anisotropy to derive information on the protein conformation. This residue-pair selection technique should simplify the study of protein structure at specific residues.