Influence of the centrosome on the structure of nucleated microtubules

The capacity of the centrosome to influence the lattice structure of nucleated microtubules was studied in vitro. Brain microtubules self- assembled to give predominantly (98%) 14-protofilament microtubules. However, under exactly the same conditions of assembly they grew off of purified centrosomes from neuroblastoma cells to give mostly (82%) 13- protofilament microtubules. Thus, the nucleation sites on the centrosome constrained the microtubule lattice to yield the number of protofilaments usually found in vivo.