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Figure 5 | BMC Structural Biology

Figure 5

From: The crystal structure of the catalytic domain of a eukaryotic guanylate cyclase

Figure 5

Communication between active sites. Plot of guanylate cyclase activity at increasing concentrations of substrate GTP. Guanylate cyclase (5 μg) was incubated for 2 min at 24 °C with the indicated concentrations of GTP in the presence of 4 mM MnCl2 and cGMP was measured. Data were fit to the equation V max ( S ) n ( S 0.5 ) n + S n MathType@MTEF@5@5@+=feaagaart1ev2aaatCvAUfKttLearuWrP9MDH5MBPbIqV92AaeXatLxBI9gBaebbnrfifHhDYfgasaacPC6xNi=xH8viVGI8Gi=hEeeu0xXdbba9frFj0xb9qqpG0dXdb9aspeI8k8fiI+fsY=rqGqVepae9pg0db9vqaiVgFr0xfr=xfr=xc9adbaqaaeGaciGaaiaabeqaaeqabiWaaaGcbaqcfa4aaSaaaeaacqWGwbGvdaWgaaqaaiGbc2gaTjabcggaHjabcIha4bqabaGaeiikaGIaem4uamLaeiykaKYaaWbaaeqabaGaemOBa4gaaaqaaiabcIcaOiabdofatnaaBaaabaGaeGimaaJaeiOla4IaeGynaudabeaacqGGPaqkdaahaaqabeaacqWGUbGBaaGaey4kaSIaem4uam1aaWbaaeqabaGaemOBa4gaaaaaaaa@4142@ , where Vmax is the maximum activity, S is the concentration of GTP, S0.5 is the substrate concentration at which half-maximal velocity is reached, and n is the Hill coefficient. From the fit, Vmax = 2795 ± 117 nmoles cGMP/min/mg, S0.5 = 269 ± 26 μM, and n = 1.49 ± 0.16. A Hill coefficient greater than 1 indicates the presence of interacting active sites.

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