FIGURE 7.

Disulfide bond formation in mutant GlyRα1 ECDs. MALDI-TOF mass spectra of unmodified tryptic fragments of different GlyRα1 ECD variants refolded under oxidative conditions. The signals corresponding to the Cys-loop (left, Cys¹³⁸–Cys¹⁵²) and GlyR-specific disulfide bond (right, Cys¹⁹⁸–Cys²⁰⁹) are shown (see Figs. 2 and 3 for reference). Mutant C41S shows unaltered cysteine bond formation as compared with the wild-type domain (WT). As expected, for mutants C138S and C152S the signal for Cys¹⁹⁸–Cys²⁰⁹ but not Cys¹³⁸–Cys¹⁵² is observed. In contrast, mutants C198S and C209S display no signal for disulfide bond formation, indicating the requirement of the GlyR-specific for the effective formation of the Cys-loop disulfide bond in vitro.