Fig. 5.
Ala substitutions at Ser-497 and either Thr-500, Ser-510, or Thr-513 have synergistic effects on the Km for GC-A. 293 cells were transiently transfected with the indicated form of GC-A and membranes from these cells were assayed for GC activity for 5 minutes in the presence of 1 μM ANP, 1 mM ATP, and increasing concentrations of GTP. (A) Comparison between WT-GC-A, GC-A-S497A-T500A, and GC-A-S497E-T500E (n = 3 from three experiments). (B) Comparison between WT-GC-A, GC-A-S497A-S510A, and GC-A-S497E-S510E (n = 3 from three experiments). (C) Comparison between WT-GC-A, GC-A-S497A-T513A, and GC-A-S497E-T513E (n = 2 from two experiments). *P < 0.0125 (significantly different from WT-GC-A). Western blots indicate the amount of protein for each form of GC-A for each experiment. Vertical bars in the symbols represent the S.E.M.