Figure 4: Changes between detached kinesin–ADP and tubulin-bound apo-kinesin.
From: The structure of apo-kinesin bound to tubulin links the nucleotide cycle to movement
(a) The α4 extension is not compatible with the structure of the β4–β5 turn in kinesin–ADP. Kinesin–ADP5 has been superimposed on nucleotide-free kinesin in the tubulin complex by overlapping common α4 residues (residues 255 to 270). Residues of the β4-β5 turn that clash with residues in the α4 extension are presented. (b) Changes in the nucleotide-binding site caused, on tubulin binding, by the rotations of the Switch I/II and P-loop subdomains. The P-loop subdomains have been superimposed to show the changes in the interactions of Asp231 with the Mg2+-coordinating ligands. For clarity, the Mg2+ coordinating water molecules are the only ones presented. (c) Kinetics of mant-ADP release from the D231A and R190A-D231A kinesin mutants. Fluorescence variations on release from the D231A (blue) and R190A-D231A (red) kinesins in the absence of microtubules (solid lines) or stimulated by 1 μM microtubular tubulin (dashed lines) are shown (10% of the experimental points are displayed) after normalization following subtraction of a linear component due to photobleaching. The line is the fit by an exponential decay function. The inset to c gives the variation of kobs as a function of microtubular tubulin concentration for both mutants.
