Abstract
Zn2+ could inhibit the anion transport activity of spectrin-stripped inside-out human erythrocyte membrane vesicles (IOVs). Removal of the cytoplasmic domain from Band 3 by trypsin could eliminate Zn2+ inhibition. The location of a Zn2+-binding site was confirmed by atomic absorbance spectrometry. The results of time-resolved fluorescence and intrinsic fluorescence quenching by KI and hypocrellin B (a photosensitive pigment obtained from a parasitic fungus growing in Yunnan, China) showed that the cytoplasmic domain is necessary for the Zn2+-induced conformational changes of the whole molecule as well as the membrane domain of Band 3. It is suggested that Zn2+ induced a conformational change in the cytoplasmic domain of Band 3, which in turn was transmitted to the membrane domain, resulting in an inhibition of activity of Band 3. Such long-range conformational changes may imply that the cytoplasmic domain is poised to function as a cytosolic arm in order to modulate the structure of the membrane domain of Band 3.