TRANSLOCATION OF MICROTUBULES CAUSED BY THE ALPHA-BETA-OUTER-ARM, BETA-OUTER-ARM AND GAMMA-OUTER-ARM DYNEIN SUBPARTICLES OF CHLAMYDOMONAS

Three kinds of subparticles of Chlamydomonas outer-arm dynein containi ng the alpha beta, beta and gamma heavy chains were isolated and assay ed for their activities to translocate microtubules in vitro. All of t hem had activities to form bundles of microtubules in solution in an A TP-dependent manner and, when adsorbed on an appropriate glass surface , translocated microtubules. The alpha beta subparticle readily transl ocated microtubules on a silicone-coated glass surface with a velocity of 4.6 mu m/second at 1 mM ATP, The beta subparticle translocated mic rotubules after it had been preincubated with tubulin dimer and when t he Brownian movement of microtubules was suppressed by addition of met hylcellulose, The velocity was on average 0.7 mu m/second. The gamma s ubparticle translocated microtubules after being preincubated with tub ulin dimer and adsorbed onto a silicone-coated glass surface. The velo city was about 3.8 mu m/second, The tubulin dimer appeared to facilita te in vitro motility by blocking the ATP-insensitive binding of dynein subparticles to microtubule, The alpha beta, beta and gamma subpartic les were thus found to have different properties as motor proteins. In addition, these subparticles showed different dependencies upon the p otassium acetate concentration. Hence the outer-arm dynein of Chlamydo monas is a complex of motor proteins with different properties.