The actomyosin interface contains an evolutionary conserved core and an ancillary interface involved in specificity

Figures

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  Fig. 1. Structure of the PfMyoA motor domain/PfAct1 filament assembly. a Representative micrograph (out of 6073) of JAS-stabilized PfAct1 filaments with bound PfMyoA motor domain. The scale bar is 50 nm. b Representative classes (out of 1534) from reference-free two-dimensional classification of segments showing lack of cooperative binding (full decoration). The scale bar is 20 nm. c Reconstruction of JAS-stabilized PfAct1 filaments (pink) with bound PfMyoA motor domain (gray). The pointed (-) end of the filament is up. d Local resolution mapped on the reconstruction. Values of color bar in Å. e Atomic temperature factors mapped on the refined model. Values of color bar in Å2 f–i Density maps and atomic model for all the actin binding elements of PfMyoA at the actomyosin interface. All the different actin binding elements are colored differently: The hypertrophic cardiomyopathy loop (HCM) in pink; Loop2 in yellow; Loop3 in dark gray; helix-turn-helix (HTH) in dark blue (see also Supplementary Fig. 1).

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  Fig. 2. Structure of the PfAct1-bound PfMyoA motor. a Atomic model of actin-bound PfMyoA motor domain with root mean square differences to the rigor-like unbound structure mapped in thickness and color, from 0–5.5 Å. Only residues present in both structures are shown. The hypertrophic cardiomyopathy loop (HCM), loop 4 (L4) and the upper and lower 50 kDa domains (U50, L50) are labeled. b Comparison of the normalized atomic temperature factors between the bound (upper panel) and unbound (lower panel) structures. The region shown corresponds to the box in A. c Density map and atomic model in the active site of PfMyoA shows without ambiguity the absence of nucleotide. There is no density in the cavity (black dashed lines) composed by the Switch-1 (green), Switch-2 (orange) and the P-loop (purple). d The density map and atomic model of the actin binding cleft located between the upper 50 kDa (U50, in blue) and the lower 50 kDa (L50, pink) domains.

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  Fig. 3. Structure of the PfMyoA-bound PfAct1 filament. a Atomic model of filamentous PfAct1 while bound to PfMyoA with root mean square differences to the bare PfAct1 filament structure mapped in thickness and color, from 0–2.5 Å. b The D-loop shows only minor structural differences in the bound (cyan) compared to the bare (chocolate red) filament (PDB code 5OGW; https://www.rcsb.org/structure/5OGW)11 with the largest difference occurring at residue E51. In the decorated filament, the conformation of the sidechain of E51 is reoriented in order to establish a polar contact of with S558 from the HTH of PfMyoA (dark blue). c The plug conformation is identical in both structures and the specific polar interactions are conserved. d Comparison of the normalized atomic temperature factors between the bound (left) and unbound (right) PfAct1structures. e Jasplakinolide (JAS) is well defined in the density map of the PfMyoA bound PfAct1 structure.

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  Fig. 4. Actomyosin interaction footprint analysis. a Overlay of the filament bound structures of PfMyoA (teal) and Myosin 6 (Myo6; red) revealing very similar orientations in relation to the filament. b Mapping of myosin footprints onto the actin filament surface. Two longitudinal neighboring actin monomers are shown. The subdomains are labeled in the upper monomer. The light blue region is contacted by all four myosins. The dark blue region is contacted by all myosins except for PfMyoA. The orange region is contacted by Myo1b and NM2c, the red region is contacted by NM2c only. c Mapping of the core (magenta) and ancillary (Anci, teal) interfaces as defined by conservation of interactions (see Supplementary Table 2) onto an open-book representation with the actin-filament surface on the left and the myosin surface on the right. The inset in the lower right corner shows the primary myosin structural elements partaking in interactions in the same orientation (HCM: hypertrophic cardiomyopathy loop; HTH: helix-turn-helix motif; A-loop: activation loop).