Structural constraints on the complex of elongation factor Tu with magnesium guanosine diphosphate from rotational-echo double-resonance NMR.

Rotational-echo, double-resonance (REDOR) NMR measurements of 31P-15N dipolar couplings have been made on a complex of Mg guanosine diphosphate (MgGDP) with uniformly 15N-labeled elongation factor Tu. The complex was embedded in a lyophilized buffer glass. The observed 15N REDOR dephasing by 31P was accounted for quantitatively by distances from 15N of Gly23 and Lys24 to P alpha and P beta of MgGDP as determined by X-ray crystallography of MgGDP complex formed using an elongation factor Tu that is missing a 15 residue loop in the vicinity of the binding site.