Fig. 5: Flexibility of the M. villosus archaellum.

a, b Atomic model showing the motion of the tail domains. Two opposite n + 10 sets of protein monomers (a) were selected and the head domains of the constituting monomers were aligned. The solid and transparent magenta models (b) were fitted into the frame 0 and frame 19 maps of the cryoSPARC 3DVA, respectively. The arrows along the tail domains in b highlight the up-down motion of the tail domains of opposite n + 10 strands. c–g Atomic models and motion trajectories showing the flexibility of the head domains along a full filament turn. Eight ArlB1 and eight ArlB2 monomers forming a full helical turn were selected (c) and their tail domains aligned. Panels d, f show the flexibility of the head domains of ArlB1 and ArlB2, respectively. Panels e, g represent the motion trajectories of the centroids (shades of blue) of each head domain. The black curve highlights the trajectory, and the dotted black line represents the filament axis. h Atomic models of one ArlB1 and one ArlB2 head domains showing their displacement during filament motion. The motion is visualised by vectors linking the backbone atoms of the atomic models fitting into the frame 0 (grey line) and frame 19 (not shown for better clarity) maps of the cryoSPARC 3DVA. i Estimation of the evolutionary conservation of AlrB1 and ArlB2. Insets focus on the hinge region. Scale bars in a and c, 50 Å; in b, d, f, h, 10 Å; in e and g, 2 Å.