CHARACTERIZATION OF A MAJOR PROTEIN IN GLUT4 VESICLES - CONCENTRATIONIN THE VESICLES AND INSULIN-STIMULATED TRANSLOCATION TO THE PLASMA-MEMBRANE

GLUT4-enriched vesicles from fat and muscle cells contain a major prot ein of 165 kDa. In the present study we have prepared GLUT4 vesicles f rom a large number of rat adipocytes, isolated the 165-kDa protein by SDS-gel electrophoresis, and obtained the sequences of four tryptic pe ptides. Comparison of the sequences with those in protein data banks s howed that the 165-kDa protein had not previously been sequenced. An a ntibody preparation against one of the peptides immunoblotted the 165- kDa protein. By this means it was found that the 165-kDa protein was c oncentrated in GLUT4 vesicles, and that insulin treatment of rat adipo cytes caused a translocation of the protein to the plasma membrane tha t paralleled the translocation of GLUT4