The effects of anion transport inhibitors on structural transitions in erythrocyte membranes.

Red blood cell membranes have been labeled with several covalent and noncovalent inhibitors of anion transport and their heat capacity profiles determined as a function of temperature. Covalent inhibitors include the amino reactive agents 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid, 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid, pyridoxal phosphate and 1-fluoro-2,4-dinitro benzene. The non-covalent inhibitors include several well known local anesthetics. The study was underataken in order to identify regions of the membrane involved in anion transport. Covalent modification in all case resulted in a large upward shift of the C transition, which is beleived to involve a localized phospholipid region. Evidence is presented which indicates that Band III protein and this phospholipid region are in close physical proximity on the membrane. Addition of non-covalent inhibitors affects the membrane in either or both of two ways. In some cases, a lowering and broadening of the C transition occurs; in others the B1 and B2 transitions are altered. These latter transitions are beleived to involve both phospholipid and protein, including Band III. These results may indicate that the non-covalent inhibitors produce their inhibitory effect on anion transport at least in part by interacting with membrane phospholipid.