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The binding of carbonic anhydrase II (CAII) to the regulatory cytosolic domain of NHE1 is reported. The results show that a novel phosphorylation-regulated CAII binding site exists in distal amino acids of the NHE1 tail and Na(super +)/H(super +) exchanger activity is linked to bicarbonate based pH regulation through carbonic anhydrase activity.

The TM7-10 region of the erythrocyte membrane anion exchanger AE1 appears to contain the active site of the protein. AE1 is inhibited by stilbene disulfonate compounds and these compounds prevented the labeling of these residues by biotin maleimide.

Interaction between the erythrocyte anion exchange membraneprotein, band 3, and a number of nonionic detergents was studied. Critical micellar concentration (cmc) values for the detergents range from 0.47 micromole to 223 millimole. Band 3 proteins aggregate Below cmc. Detergent concentrations 2-200 times the cmc are needed to inhibit aggregation. Detergents with alkyl chains of eight carbons or less denature band 3 while detergents with alkyl chains of 12 carbons or more preserve the structure of band 3.

A concatamer of AE1, which is present in the erythrocyte plasma membrane as a noncovalent dimer and has facilitated transmembrane [Cl.sup.-]/HC[O.sub.3.sup.-] exchange, is designed to facilitate fluorescence resonance energy transfer (FRET) studies. Two distance constraints are provided for the position of Q434, which is located in extracellular loop 1, connecting the first two transmembrane segments of AE1.

The physical and functional interactions of Carbonic anhydrase IV and the Human NBC1 sodium/bicarbonate co-transporter are examined. Sodium/bicarbonate co-transporters (NBC) are crucial in the regulation of intracellular pH and HCO3 metabolism.

Examines changes in the regions of AE1, a chloride/bicarbonate anion exchanger of erythrocyte membrane during the binding of 4,4'-dinitrostilbene-2,2'-disulfonate (DNDS). Effect of DNDS on AE1 transport during biotin maleimide labeling; Effects of biotinylation mutant reductions; Substrate and DNDS binding regions of AE1.