ACTIVATION OF GLUCOSE DIFFUSION FROM EGG LECITHIN LIQUID CYRYSTALS BY SERUM ALBUMIN

The diffusion of [14C]glucose from phospholipid model membrane systems has been measured in the presence and absence of bovine serum albumin under various conditions. At acid pH, bovine serum albumin enhances the rate at which glucose diffuses from lecithin-cholesterol-dicetyl phosphate micelles. The enhancement effect has a pK of 4.3. This is close to the pH at which the well-known acid conformation change occurs in this protein. The activation of diffusion only takes place with negatively charged micelles, and is not disrupted by high salt concentrations. The effects of temperature and protein concentration on the diffusion rate were also studied. It is suggested that the protein binds through electrostatic interactions initially, but that the subsequent formation of apolar bonds brings about the activation of glucose diffusion. © 1969.