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. 2009 Apr 2;28(10):1518–1530. doi: 10.1038/emboj.2009.86

Figure 6.

Figure 6

The E757Q mutation destabilizes dimer assembly. (A) Responses to 100-ms applications of 10 mM glutamate for -HERLK- and -HERLKQ illustrating the five-fold faster rate of onset of desensitization due to E757Q substitution. (B) Sedimentation equilibrium scans for -HERLKQ at 1 mg ml−1 and 24 000 r.p.m. analyzed identically as for -HERLK- (Figure 3C); the dimerization Kd decreases ∼6-fold to 628 μM. (C) Base of helix J tilts by 5° in -HERLKQ; dimer assemblies for -HERLKQ (red) and -HERLK- (gold) were superimposed by least-squares using D1 Cα coordinates; the solid line shows a Cα trace illustrating that movement is limited to the base of helix J. (D) Residues at the base of helix J and in the linker leading to helix K are disordered in -HERLKQ. An Fo−Fc omit electron density map contoured at 3.5σ was calculated with residues Glu756–Lys759 omitted from the Fc calculation; stick representation for these residues show main chain alternative conformations for Glu756, E757Q and Gly758, and side-chain alternative conformations for Glu756, E757Q and Lys759.