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. 2011 Nov 17;287(2):1022–1031. doi: 10.1074/jbc.M111.284067

FIGURE 3.

FIGURE 3.

The functional coupling of permanent and transient core residues Ser-288 and Ala-291 in Af1503 and Ile-226 and IIe-229 in Tsr. A, shown are serine responses of the A291I, S288I, and S288I/A291I mutants in the Af1503 HAMP. S288I and A291I were not regulated. With the double mutant S288I/A291I, regulation by serine is gained. Maximal inhibition was 59 ± 1.6%. Basal activities of the S288I, A291I, and S288I/A291I mutants were 3.4 ± 0.3, 21.5 ± 2.4, and 17.7 ± 1.5 nmol of cAMP·mg−1min−1, respectively. B, shown are serine responses of Tsr HAMP mutants I226S, I229A, and I226S/I229A. Basal activities were, respectively, 20 ± 1, 3.4 ± 0.5, and 5.1 ± 0.4 nmol of cAMP·mg−1min−1. Maximal serine inhibition was 70 ± 6% for the double mutant and 65 ± 11% for the I226S mutant. The mutation S229I disrupted serine regulation. Western blots (0.5 μg of membrane preparation) indicated similar expression levels for all mutants and no proteolysis of the recombinant proteins.