Fig. 2.
Effects of cAMP, (Rp)-cAMPS, and (Sp)-cAMPS on the stopped-flow kinetics of FM-R92C RIα(91–244) binding to the C-subunit. Top left, control. Top right, in the presence of 10 μm cAMP. Bottom left, in the presence of 100 μm (Rp)-cAMPS. Bottom right, in the presence of 100 μm (Sp)-cAMPS. Stopped-flow traces of FM-R92C-RIα(91–244) rapidly mixed with C-subunit in the absence of cAMP are shown. The final concentration of FM-RIα(91–244) R92C was 100 nm, and the concentration of the C-subunit was varied from 1 to 6 μm. The decreasing emission follows the time course of binding. The solid lines denote the best fit of the data to a single exponential equation. Samples were suspended in a buffer containing 50 mm MOPS, pH 7.0, 50 mm NaCl, 1 mm DTT, 2 mm MgCl2, and 0.2 mm ATP at 22 °C. A.U., absorbance units.