Fig. 4.

CN2-Cbi does not require the sGC regulatory region and does not decrease GTP K_m. A, schematic representation of the domain structure of the wild-type α1β1 and the truncated αΔ269βΔ200 sGC. The domain structure is adapted from Ma et al. (2008). Coil-coil elements (CC) and the HNOX-associated PAS-like domain (HNOX-A) are involved in dimerization. The heme-NO/oxygen-binding domain of the β subunit (HNOX-β) binds heme. GC-CD, guanylyl cyclase catalytic domains; NH2-dom-α, amino-terminal domain of the α subunit. B, cGMP-forming activity in 100,000g supernatants of Sf9 cells expressing wild-type (□) or truncated αΔ269/βΔ200 (■) sGC was tested under basal conditions in the presence of 4 mM Mn²⁺, 100 μM CN2-Cbi, 40 nM BAY58-2667, or 2 μM BAY41-2272. Data are presented as means ± S.D. of two independent preparations assayed in triplicate. ns, difference is not statistically significant; *, p < 0.05. C, effect of CN2-Cbi on the GTP K_m. Lineweaver-Burk double-reciprocal plots of the basal (♦) and 100 μM CN2-Cbi (▴)-stimulated sGC activity (V_a) are shown. sGC activity was determined using the 7.25 to 2000 μM range of GTP concentrations. Summarized data of two independent experiments performed in triplicate are shown.