Figure 4.

Comparison of the localization N terminus of MyBP-C within the actin lattice in active and relaxed muscle sarcomeres with in silico models with known binding geometries. (A) Illustrative representations of MyBP-C’s three binding partner interactions considered using in silico models. (B) In silico image generated with 20% of MyBP-C N termini bound to actin filaments and the remaining molecules randomly distributed in the space between the thick and thin filament surfaces. Dashed line and yellow arrow demonstrate the generation of the radial intensity profile plotted in C. (C) Radial intensity profiles of the fluorescence intensity of MyBP-C’s N terminus between the center of the actin hexagon and vertices of the actin filaments in the in silico image shown in B (dashed line) and the experimental data for the active (red line) and relaxed (black line) muscle preparations. (D) RMSDs between the radial intensity profiles, as shown in C, of the active (red) and relaxed (black) muscle images and the in silico images generated with a fraction of MyBP-C N termini bound to a binding partner (Fig. S6, Fig. S7, and Fig. S8). Error bars represent the SEM of the RMSDs from six in silico images generated for each condition. (E) Merged images for sixfold rotational average of all actin (green) and MyBP-C (magenta) images. The brightness and contrast of the image were adjusted to present the brightest spots in the images. Scale bars, 25 nm. a.u., arbitrary unit.