Identification of three coated vesicle components as alpha- and beta-tubulin linked to a phosphorylated 50,000-dalton polypeptide.
Coated vesicles are involved in the intracellular transport of membrane proteins between a variety of membrane compartments. The coats of bovine brain coated vesicles contain at least six polypeptides in addition to an 180,000-dalton polypeptide called clathrin. In this report we show that the 54,000- and 56,000-dalton coated vesicle polypeptides are alpha- and beta-tubulin, determined by immunoblotting and two-dimensional gel electrophoresis. An affinity-purified tubulin antiserum can precipitate coated vesicles. The tubulin polypeptides are tightly associated with a 50,000-dalton coated vesicle polypeptide, which is phosphorylated. The phosphorylated 50,000-dalton polypeptide appears to be related to brain microtubule-associated tau proteins since it can be specifically immunoprecipitated by an affinity-purified antiserum directed against these proteins. In addition, gel filtration experiments indicate that at least a fraction of the 50,000-dalton polypeptide may associate with the 100,000-dalton coated vesicle polypeptide. Since brain is a tissue rich in tubulins, liver coated vesicles were analyzed for the presence of alpha- and beta-tubulin. Like brain coated vesicles, liver coated vesicles also contain an endogenous kinase activity, which phosphorylates polypeptides of the same molecular weights and isoelectric points as the brain coated vesicle 50,000-dalton, tau-like polypeptide, and alpha- and beta-tubulin. The phosphorylated 50,000-dalton polypeptide may link the membrane and contents of coated vesicles with components of the cytoskeleton.
D033942:Adaptor Proteins, Vesicular Transport; D000818:Animals; D001921:Brain; D002417:Cattle; D055598:Chemical Phenomena; D002621:Chemistry; D011992:Endosomes / Q000032:analysis*; D008099:Liver; D008970:Molecular Weight; D010750:Phosphoproteins / Q000032:analysis*; D010766:Phosphorylation; D011506:Proteins / Q000032:analysis* / Q000378:metabolism; D014404:Tubulin / Q000032:analysis* / Q000378:metabolism; D016875:tau Proteins
D033942:Adaptor Proteins, Vesicular Transport; D010750:Phosphoproteins; D011506:Proteins; D014404:Tubulin; D016875:tau Proteins