Microtubule-associated proteins and microtubule-based translocators have different binding sites on tubulin molecule.
It has been previously shown that a class of microtubule proteins, the so-called microtubule-associated proteins (MAPs), binds to the C-terminal part of tubulin subunits. We show here that microtubules composed of tubulin whose 4-kDa C-terminal domain was cleaved by subtilisin (S-microtubules) are unable to bind MAPs but can still bind the anterograde translocator protein kinesin and the retrograde translocator dynein. Binding of both motors to S-microtubules, like their binding to normal microtubules, was ATP-dependent. In addition, direct competition experiments showed that binding sites for kiensin and MAPs on the microtubule surface lattice do not overlap. Furthermore, S-microtubules stimulated the ATPase activity of kinesin at least 8-fold, and the affinities of kinesin for control and S-microtubules were identical. S-microtubules were able to glide along kinesin-coated coverslips at a rate of 0.2 microns/s, the same rate as control microtubules. We conclude, that unlike MAPs, kinesin and cytoplasmic dynein bind to the tubulin molecule outside the C-terminal region.
Rodionov
V I
VI
A. N. Belozersky Laboratory of Molecular Biology and Bioorganic Chemistry, Moscow State University, Union of Soviet Socialist Republics.
Gyoeva
F K
FK
Kashina
A S
AS
Kuznetsov
S A
SA
Gelfand
V I
VI
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D001921:Brain / Q000648:ultrastructure; D001923:Brain Chemistry; D002417:Cattle; D004398:Dyneins / Q000378:metabolism*; D016547:Kinesins; D008854:Microscopy, Electron; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism; D013381:Subtilisins / Q000378:metabolism; D014404:Tubulin / Q000378:metabolism*
D008869:Microtubule-Associated Proteins; D014404:Tubulin; D000255:Adenosine Triphosphate; D013381:Subtilisins; D000251:Adenosine Triphosphatases; D004398:Dyneins; D016547:Kinesins