TUBULIN REQUIRES TAU FOR GROWTH ONTO MICROTUBULE INITIATING SITES

Tubulin [porcine brain] purified by phosphocellulose chromatography and free of accessory proteins will not form microtubules in the absence or presence of microtubule initiating sites (flagellar microtubules). The capacity for growth onto pre-existing seeds can be restored by the addition of small quantities of partially purified tau[.female.] protein. Larger quantities restore the capacity for spontaneous assembly. Tubulin probably requires .female. for both initiation and growth of microtubules may be incorporated into the microtubule throughout its length.