Fig. 4. Subcellular fractionation of Syt V and Syt IX in INS-1E cells. Subcellular fractions of INS-1E cells were obtained using the sucrose density gradient described in Materials and Methods. Aliquots of each fraction of the gradient were analysed by western blotting using antibodies directed against Na⁺/K⁺-ATPase, synaptophysin (SVP38), carboxypeptidase H (CPH), Syt V and Syt IX. Sucrose concentration was calculated from the refractive index of the fractions. The top panel shows the amount of insulin present in the fractions corresponding to the distribution of insulin-containing secretory granules.