Affinity of hemoglobin for the cytoplasmic fragment of human erythrocyte membrane band 3. Equilibrium measurements at physiological pH using matrix-bound proteins: the effects of ionic strength, deoxygenation and of 2,3-diphosphoglycerate.

摘要: Abstract The cytoplasmic fragment of band 3 protein isolated from the human erythrocyte membrane was linked to a CNBr-activated Sepharose matrix in an attempt measure, batch experiments, its equilibrium binding constant with oxy- and deoxyhemoglobin at physiological pH ionic strength values presence or absence 2,3-diphosphoglycerate. All experiments were done 7.2, constants computed on basis one hemoglobin tetramer bound per monomer fragment. In 10 m M -phosphate buffer, dissociation K D = 2 × −4 measured for oxyhemoglobin shown increase 8 50 -NaCl. Association could not be demonstrated higher salt concentrations. Diphosphoglyeerate-stripped associate more strongly 3. -bis-Tris (pH 7.2) 120 -NaCl, 4 > measured. Upon addition increasing amounts 2,3-diphosphoglycerate, complex formed between dissociated. On reasonable assumption that site present modified upon linking matrix, results indicated diphosphoglycerate-stripped partially liganded tetramers T state bind inside intact red blood cell.