Quantitative determination, isolation and characterization of pig lung tubulin

Tubulin from pig lung was quantitatively determined, isolated and characterized. It accounted for about 0.3-0.4% of the total soluble protein of pig lung, as measured by colchicine binding or radioimmunoassay. Purified tubulin was obtained by several cycles of polymerization and depolymerization in the presence of dimethyl sulphoxide and 2H2O as stabilizing agents. The proteolytic cleavage patterns of the lung tubulin subunits closely resembled those of other mammalian cytoplasmic tubulin subunits, such as those of brain and kidney. However, the pattern of lung isotubulins on isoelectric focusing differed substantially from that of brain isotubulins . These differences did not appear to be the result of major lung tubulin post-translational modifications, since approximately the same pattern of isotubulins was found for the tubulin synthesized by lung poly(A)-containing mRNA in a reticulocyte system in vitro.