Irreversible inactivation of red cell chloride exchange with phenylglyoxal, and arginine-specific reagent

Chloride exchange in resealed human erythrocyte ghosts can be irreversibly inhibited with phenylglyoxal, a reagent specific for the modification of arginyl residues in proteins. Phenylglyoxal inhibits anion transport in two distinct ways. At 0 degrees C, inhibition is instantaneous and fully reversible, whereas at higher temperature in an alkaline extracellular medium, covalent binding of phenylglyoxal leads to an irreversible inhibition of the transport membranes system. Indiscriminate modification of membrane arginyl residues was prevented by reacting the with phenylglyoxal in an alkaline extracellular medium while maintaining intracellular pH near neutrality. The rate of modification of anion transport depends on phenylglyoxal concentration, pH, temperature, and the presence of anions and reversible inhibitors of the anion transport system in fashions that are fully compatible with the conclusion that phenylglyoxal modifies arginyl residues that are essential for anion binding and translocation. Phenylglyoxal reacts rapidly with the deprotonated form of the reactive groups. It is proposed that the effects of anions and of negatively charged transport inhibitors on the rate of irreversible binding of phenylglyoxal are related to the effects of the anions on a positive interfacial potential. This potential determines the local pH, and thereby the concentration of deprotonated groups, in an exofacial region of the anion transport protein.