Structure of the human nonmuscle myosin 2A motor domain: Insights into isoform-specific mechanochemistry

Figures

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  Figure 1. Structure of the NM2A motor domain with an artificial lever arm. Ribbon representation of the NM2A-2R structure with subdomains color-coded as follows: Upper 50 kDa domain (light green), lower 50 kDa domain (dark green), converter (red), SH3-domain (orange), and artificial lever (blue). NM2A, nonmuscle myosin 2A; SH3, Src homology 3

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  Figure 2. Comparison of NM2A with NM2B and NM2C.A, overlay of NM2A with NM2B (PDB: 4PD3, left) and NM2C (PDB: 5I4E, right) motor domains. Differing residues are highlighted in red. NM2B and NM2C are shown at 50% transparency (light gray and light blue, respectively); NM2A is colored by domain. NM2A and NM2B are in the rigor state; NM2C is in the pre-powerstroke (ATP) state. B, RMSD values for motor domain subdomains after alignment. Below the values, overlays of the corresponding subdomains are shown using the same color scheme. NM2A, nonmuscle myosin 2A; PDB, Protein Data Bank.

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  Figure 3. Interaction of NM2s with ATP.A, ATP-binding sites shown as three-dimensional models (upper panels) and two-dimensional interaction diagrams (lower panels). B, minimum distances between ATP and interacting residues in the adenine recognition site, P-loop, and wwitch-1. Data are means ± S.D., averaged over the final 100 ns of each simulation and three independent replicates. No statistically significant differences were detected. NM2, nonmuscle myosin 2.

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  Figure 4. Interaction of NM2 isoforms with the actin filament. A, crystal structure of the apo-state NM2A motor domain (colored as in Fig. 1) docked into the myosin density of the actomyosin complex (yellow, cutoff 3σ; EMDB: EMD-8164; PDB: 5JLH). The actin filament is shown in gray. B, average RMSD ± SD of NM2A (red), NM2B (blue), and NM2C (green) in simulations starting from the apo motor domains positioned near the actin filament (dark shades) or in isolation (light shades). The asterisk (∗) marks termination of a shorter trajectory. C, starting interaction of the NM2A apo motor domain positioned near the actin filament (gray) with actin-interacting regions highlighted: loop4 (red), CM-loop (orange), helix–turn–helix (blue), loop3 (green), and loop2 (brown). D, RMSF of NM2A, NM2B, and NM2C in the presence and absence of actin. Motor domain regions involved in actin binding are color-coded as in panel C, and isoforms are colored as in panel B. E, sequence alignment of actin-interacting regions from NM2A, NM2B, and NM2C. Conservation is indicated by asterisks (∗) for identity, colons (:) for strong similarity, and periods (.) for weak similarity. NM2A, nonmuscle myosin 2A; PDB, Protein…