Kinetic parameters of MsGC-β3 and MsGC-β3ΔC338
| . | Vmax (pmoles min-1 mg-1 protein) . | . | Km (mmol l-1) . | . | Hill coefficient . | . | |||
|---|---|---|---|---|---|---|---|---|---|
| . | MgCl2 . | MnCl2 . | MgCl2 . | MnCl2 . | MgCl2 . | MnCl2 . | |||
| MsGC-β3 | 62.3±11.2 | 39.0±5.0 | 2.62±0.81 | 0.13±0.07 | 0.90±0.06 | 1.01±0.06 | |||
| MsGC-β3ΔC338 | 77.0±4.7 | 47.9±3.7 | 0.40±0.08 | 0.22±0.05 | 1.16±0.13 | 0.89±0.06 | |||
| ANOVA | NS | NS | P<0.001 | NS | NS | NS | |||
| MsGC-β3ΔC29 | 26.8±0.9 | ND | 0.27±0.03 | ND | 1.03±0.07 | ND | |||
| . | Vmax (pmoles min-1 mg-1 protein) . | . | Km (mmol l-1) . | . | Hill coefficient . | . | |||
|---|---|---|---|---|---|---|---|---|---|
| . | MgCl2 . | MnCl2 . | MgCl2 . | MnCl2 . | MgCl2 . | MnCl2 . | |||
| MsGC-β3 | 62.3±11.2 | 39.0±5.0 | 2.62±0.81 | 0.13±0.07 | 0.90±0.06 | 1.01±0.06 | |||
| MsGC-β3ΔC338 | 77.0±4.7 | 47.9±3.7 | 0.40±0.08 | 0.22±0.05 | 1.16±0.13 | 0.89±0.06 | |||
| ANOVA | NS | NS | P<0.001 | NS | NS | NS | |||
| MsGC-β3ΔC29 | 26.8±0.9 | ND | 0.27±0.03 | ND | 1.03±0.07 | ND | |||
COS-7 cells were transiently transfected with MsGC-β3,MsGC-β3ΔC338 or MsGC-β3ΔC29 as described in Materials and methods. Cell extracts were assayed for guanylyl cyclase activity in the presence of different concentrations of GTP and 4 mmol l-1MgCl2 or 4 mmol l-1 MnCl2. For each GTP concentration, samples were incubated for 5, 15 and 30 min to ensure linearity of the rate of cGMP formation.
Values for Vmax and Km for MsGC-β3 and MsGC-β3ΔC338 were calculated from the data shown in Fig. 6A,B.
The Hill coefficient was calculated as the slope of the line produced by plotting log[rate/(Vmax—rate)] versuslog[GTP].
A similar set of experiments was carried out using MsGC-β3ΔC29 but the data is not included in the graphs in Fig. 6.
NS, not significant; ND, not determined.