Tubulin synthesis on polysomes isolated from brain and leg muscle of embryonic chick.

A protein-synthesizing system has been established in vitro, in which tubulin is synthesized on polysomes isolated from brain and leg muscle of embryonic chick. The tubulin synthesized in vitro is characterized by (i) its electrophoretic mobility on sodium dodecyl sulfate-acrylamide gels (brain: 55,000 daltons; leg muscle: 53,000 daltons), and (ii) its ability to function as a microtubular subunit, as judged by its specific ability to participate in at least two polymerization and depolymerization steps in the microtubule assembly system in vitro.