Figure 4.

Effects of S133D mutation to mimic P/A linker phosphorylation on the TPA of actin. A, domain organization of N-terminal cMyBP-C constructs C0–C2 and C0–C2 S133D. The Asp for Ser substitution (D) is at the putative GSK3β phosphorylation site in the P/A linker. B, binding of C0–C2 constructs to 1 μm phalloidin-stablized ErIA-actin. C, angular amplitude (°) of actin as a function of v, the fraction bound to N-terminal cMyBP-C. Curves show fits of a cooperativity model to determine n (χ² = 4 and 9 for C0–C2 and C0–C2 S133D, respectively. For reference, for linear fits χ² = 25 and 27, respectively.). D, rates of rotational motions (radians/ms) as a function of v, the fraction bound, and fit to a cooperativity model to determine n. Error bars denote ± S.E.