Such inhibitory gating processes include (i) blocking of ADP release by the "tethered" head until nucleoside triphosphate binds to the "bound" head (9, 11, 21) and (ii) slowing of ATP binding to the leading head when the neck linker in the trailing head is docked (22, 23).
Of the 221 2-headed cross-bridges, 140 had both heads strongly attached (Fig. 1D, H, I-left side, K, L), 55 had one strongly and one weakly bound head (Fig. 1G, J), and 26 had both heads weakly bound (Fig. 1I - right side).
Once the bound head hydrolyzes ATP, fully docks its NL, and the tethered head binds the MT, the motor enters a mechanically strained, two-heads-bound (2-HB) state (Rice et al., 1999; Rosenfeld et al., 2003; Block, 2007; Yildiz et al., 2008; Gennerich and Vale, 2009; Clancy et al., 2011).
However, if the tethered head reaches the forward MT binding site and completes the step before the bound head can dissociate, kinesin enters the two-heads-bound (2-HB) state.
In WT kinesin, an essential difference between the 2-HB state [C] and the 1-HB state with the tethered head positioned in front of the bound head [B] is that inter-head tension can develop only when both heads are strongly bound.
In these assays, we bound the mant-ADP charged Head3/Neck1 chimera to microtubules and waited until equilibrium, which resulted in the release of one mant-ADP ligand from the bound head.
Nevertheless, every morning dozens of new corpses appeared in the streets, many of them frozen in their final moments: hands bound, heads bagged, burned with acid, drilled with holes.
The distribution of lever arm azimuths is widest for strongly bound heads and smaller for weakly bound heads.
The number of strongly bound heads is 1082 representing 29% of the total available.
The S1 S2 junctions for all but two of the quasiatomic models for strongly bound heads are positioned anticlockwise from this line.
Beausang et al. [84] indicated that the visibility of actin filament rotation in motility assays depends on the number of rigor bound heads providing a drag force to slow filament movement.
