Figure 3.

Sequence requirements for monastrol binding to Eg5. (A) Amino acid sequence alignment of residues near the monastrol binding site in Eg5 homologs from Homo sapiens, Xenopus laevis, Danio rerio, Drosophila melanogaster, Aspergillus nidulans and the corresponding residues in human conventional kinesin (Kif 5B). Residues that are conserved among monastrol-sensitive species [7, 27, 28] are highlighted in yellow in all homologs where they are identical. Amino acid side chains expected to occlude the drug binding site are highlighted in red. (B) Measuring ATP hydrolysis by 400 nM hEg5-367H (circles) or 620 nM Klp61F-364H (squares) in the presence of 1 mM ATP over a range of (S)-monastrol concentrations. Each data point is the average of three independent experiments. The IC₅₀ for (S)-monastrol for Eg5 and Klp-61F are 6.1 +/- 0.7 and 230 +/- 4 μM, respectively.