Colchicine binding activity of rat brain polysomes.

In this communication, we report the presence of a unique colchicinebinding activity in the polysomes of rat brain. This drug-binding property, is somewhat similar to that of tubulin isolated from many sources; however, it differs in several biochemical characteristics such as (i) thermal stability of colchicine-binding site, (ii) protection of binding site by vinblastine and (iii) time required for binding equilibration. Such binding of colchicine to the polysomes is most probably due to the presence of a nascent peptide chain of tubulin in the polysome.