Fig. 2. Glycine concentration-response curves of wild-type and GluN1 mutant receptors: (A ) wild-type GluN1/2A receptors, (B ) GluN1 (W731A)/2A mutant receptors, (C ) GluN1(W731L)/2A mutant receptors, (D ) GluN1(F758A)/2A mutant receptors, (E ) GluN1(F758L)/2A mutant receptors, and (F ) GluN1(F758W)/2A (blue squares ) and GluN1(F758Y)/2A (green circles ) mutant receptors. The curves shown are fit to the Hill equation. The points are mean values from an average of nine cells; the error bars are standard errors. Data have been normalized to the highest saturating glycine concentration for each receptor.