Volume 24, Issue 11, Pages 2000-2007 (November 2016) A Highly Conserved Yet Flexible Linker Is Part of a Polymorphic Protein-Binding Domain in Myosin-Binding Protein C  Katharine A. Michie, Ann H. Kwan, Chang-Shung Tung, J. Mitchell Guss, Jill Trewhella  Structure  Volume 24, Issue 11, Pages 2000-2007 (November 2016) DOI: 10.1016/j.str.2016.08.018 Copyright © 2016 Elsevier Ltd Terms and Conditions

Structure 2016 24, 2000-2007DOI: (10.1016/j.str.2016.08.018) Copyright © 2016 Elsevier Ltd Terms and Conditions

Figure 1 Bioinformatics Results (A) Schematic of cMyBP-C. (B) Clustal Omega alignments of PSI-BLAST search data showing the conservation analysis (threshold 40%) of ΔmC2 from Jalview (ClustalX coloring). Numbering refers to the human cardiac MyBP-C sequence. (C) Secondary structure and disorder predictions (H, helix; E, β sheet; D, disorder). See also Tables S1 and S2. Structure 2016 24, 2000-2007DOI: (10.1016/j.str.2016.08.018) Copyright © 2016 Elsevier Ltd Terms and Conditions

Figure 2 NMR Results (A) Ribbon diagram of ΔmC2. The THB (blue), the flexible linker (shown as an extended structure, cyan), and the C2 domain (magenta). Gray spheres indicate locations of mutations in Table S1. (B) The 20 lowest energy structures aligned via the THB (blue cartoon) or C2 (magenta cartoon). (C) Weighted chemical shift changes as Δδ ppm (HN, N) for assigned residues of 15N-labeled ΔmC2 or CaM. Significant changes (red vertical bars) are Δδ values that are 1 or more SD greater than the mean (horizontal red line). Blue bars indicate residues with Δδ values too large to be traced or they disappeared during titration. Yellow bars represent prolines that lack amide protons so provide no data. See also Figures S1, S2, and S4 and Tables S1 and S3. Structure 2016 24, 2000-2007DOI: (10.1016/j.str.2016.08.018) Copyright © 2016 Elsevier Ltd Terms and Conditions

Figure 3 SAXS Results (A) I(q) versus q for ΔmC2 (magenta), CaM (wheat), and CaM-ΔmC2 (gray) complex, error bars are 1 SD of propagated counting statistics, although mostly they are smaller than the symbols used to represent the data points. The black line overlaid with the data for ΔmC2 is the ensemble optimization model (EOM) fit to those data. The inset shows Guinier plots with line fits for qRg < 1.3, for the same datasets using the same color key. Data are on an absolute scale, with I(q) values for ΔmC2 and CaM divided by 4 and 2, respectively, for clarity. (B) P(r) versus r corresponding to the I(q) profiles in (A) with the same color key. (C) Ab initio bead models optimized to fit the data in (A) with corresponding color key. (D) Overlay of semi-transparent ab initio models in (C) in two orientations with a cartoon representation of the CaM-ΔmC2 model from Figure 4A. The cartoon representation uses the same color coding as Figure 2 for ΔmC2, with CaM as wheat. The transparent magenta surface results in a red hue to parts of the wheat-colored CaM. See also Table S4 and Figure S3. Structure 2016 24, 2000-2007DOI: (10.1016/j.str.2016.08.018) Copyright © 2016 Elsevier Ltd Terms and Conditions

Figure 4 CaM-ΔmC2 Models and Fits to Scattering Data (A and B) CaM-ΔmC2 model built starting with PDB: 2KDU (A) model 5 and (B) model 1 with key contact residues between Δm and CaM highlighted. CaM (wheat colored) is shown as a surface representation, while ΔmC2 is shown as a cartoon with Δm having the same color coding as in Figure 2A. (C) CRYSOL calculated model I(q) fits to the scattering data (black squares, error bars are 1 SD of propagated counting statistics, although mostly they are smaller than the symbols used to represent the data points) for the models in (A) (white line) and (B) (yellow line). Scattering data and model fits are on an absolute scale, with those for model fit (B) multiplied by 5 for clarity. (D) Overlay of the two models in (A) and (B) in a cartoon representation. Color coding is dark blue/cyan/magenta/wheat or light blue/teal/light pink/orange for the THB, linker, and CaM for models in (A) and (B), respectively. Ser362 is highlighted as cyan spheres, and the CaM-bound Ca2+ as yellow spheres. See also Tables S4 and S5 and Figures S4 and S5. Structure 2016 24, 2000-2007DOI: (10.1016/j.str.2016.08.018) Copyright © 2016 Elsevier Ltd Terms and Conditions