Required for insulin-stimulated glucose transport and glucose transporter SLC2A4/GLUT4 translocation from intracellular glucose storage vesicle (GSV) to the plasma membrane (PM) in adipocytes. Binds phospholipid membranes in a calcium-dependent manner and is necessary for the optimal membrane fusion between SLC2A4/GLUT4 GSV and the PM. Binds 3 Ca(2+) ions per C2 domain. Dynamically associated with GLUT4-containing glucose storage vesicles (GSV) and plasma membrane in response to insulin stimulation. Expressed in liver, muscle and fat. The C2 domain binds to calcium and membrane lipids. Phosphorylated on Ser-197 by active myristoylated kinase AKT2; insulin-stimulated phosphorylation by AKT2 regulates SLC2A4/GLUT4 translocation into the plasma membrane. Extended N-terminus.