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Figure 4.
The conformational change in KCBP accompanying ATP
hydrolysis. (A) The structure of KCBP-KIC complex is superposed
with the structure of KCBP alone (PDB ID code 3cob, chain A).
Only the switch II helix α4 and the regulatory elements (in
pink) of the solo KCBP structure are shown. The analogous
elements of KCBP in the structure of the complex are highlighted
in orange. For our previous crystallographic studies of KCBP
(PDB ID codes 1sdm, 3cob, 3cnz), we used KCBP from potato (amino
acids 884-1252) that is 80% identical to Arabidopsis KCBP. (B)
The hydrophobic pocket (marked in yellow) on the kinesin surface
(gray) is occupied by Ile-1210 in the ATP-like conformation. (C)
The shifted hydrophobic pocket (marked in yellow) on the kinesin
surface (gray) is occupied by Ile-890 of the β1 strand as found
in the ADP state. Ile-1210 is expelled from the hydrophobic
pocket on the kinesin surface and interacts with KIC (Fig. 3).
Hydrophobic residues are conserved at positions 890 and 1210 in
all kinesins. Helices α4 and α6 and the β1 strand of KCBP
(indicated) are shown schematically and are visible through the
translucent surface. The neck mimic is shown as a coil and is
colored according to the conformational state.
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