Figure 8.

In Vitro Binding of Microtubules by the FRA1 Motor Domain.

The FRA1 motor domain fused with maltose binding protein was assayed for its ability to bind microtubules in the microtubule cosedimentation assay. After sedimentation, the fusion protein remained in the supernatant fraction in the absence of microtubules (lanes 1 and 2), whereas a large fraction of the fusion protein cosedimented with microtubules in the presence of microtubules (lanes 3 and 4). The addition of ATP significantly reduced the cosedimentation of the fusion protein with microtubules (lanes 5 and 6), and the nonhydrolyzable ATP analog adenylylimidodiphosphate (AMP) had no effect on the cosedimentation of the fusion protein with microtubules (lanes 7 and 8). MT, microtubule; P, pellet; S, supernatant; Tub, tubulin.