Sulfate transport by band-3 protein in adult human erythrocytes was shown to be modulated by oxygen pressure. In particular, a higher transport activity was measured under high oxygen pressure than at low one (0.0242+/-0.0073 vs. 0.0074+/-0.0010 min(-1)). Other factors, such as magnesium ions and orthovanadate, which can indirectly affect the binding properties of the cytoplasmic domain of band 3 (cdb3), influence significantly the anion exchanger activity. No effect of oxygen pressure on sulfate transport was found in chicken erythrocytes, which may be related to their lacking the cdb3 binding site. These findings are fully consistent with a molecular mechanism where the oxygen-linked transition of hemoglobin (T-->R) could play a key role in the regulation of anion exchanger activity.