KINESIN DOES NOT SUPPORT THE MOTILITY OF ZINC-MACROTUBES

Moving along a microtubule, kinesin follows a course parallel to the p rotofilaments; but it is not known whether kinesin binds exclusively o n a single protofilament. The presence of zinc during tubulin polymeri zation induces sheets where neighboring protofilaments are antiparalle l. If kinesin could support the motility of these zinc-sheets, then th e binding site for a kinesin molecule would be limited to a single pro tofilament. Kamimura and Mandelkow [1992: J. Cell Biol. 118:865-75] re ported that kinesin moves along zinc-sheets. We found that zinc-sheets grown under their conditions often had a microtubule-like structure a long one edge. We confirmed the possibility that the motility observed by Kamimura and Mandelkow [1992: J. Cell Biol. 118:865-75] is attribu ted to the microtubule-like structure rather than the zinc-sheet. To r esolve the question of whether kinesin can recognize an antiparallel p rotofilament lattice, we investigated the kinesin-mediated motility of zinc-macrotubes. At higher free zinc concentrations, zinc-sheets roll up as macrotubes, free of edges. In the presence of 10 mu M taxol and 100 nM free Zn2+ at pH 6.8, the samples were shown by electron micros copy to contain only macrotubes. Under these buffer conditions, kinesi n could bind strongly to axonemal doublets in the presence of AMP-PNP, and generate motility in the presence of ATP, but kinesin did not bin d to nor move the macrotubes. This shows that kinesin cannot bind effi ciently to nor move on the anti-parallel lattice; it is possible (thou gh not necessary) that the groove between two parallel protofilaments is required for kinesin's motility. (C) 1995 Wiley-Liss, Inc.