Effects of 2,3-diphosphoglyceric acid on the human erythrocyte membrane phosphorylation system

Effect of intracellular pH changes on the distribution of tyrosine- and serine/threonine-protein kinase activities in human erythrocytes

The pH-dependence of the distribution of Tyr- and Ser/Thr-protein kinases between cytosol and membrane in human erythrocytes was investigated. When the internal pH of human erythrocytes is decreased from 8 to 7.3 the membrane-associated Tyr-protein kinase activity markedly increases at expense of the cytosolic counterpart, whereas the membrane-bound and cytosolic casein kinase activity are unaffected. This different response of the two kinase activities to the imposed variation of intracellular pH may explain why the Tyr-phosphorylation of cytoplasmic domain of band 3 results to be much higher in the ghosts from erythrocytes whose internal pH was 7.3 than that in the ghosts from erythrocytes whose internal pH was 8. By contrast, the Ser-phosphorylation of spectrin beta-subunit (band 2) and band 3 results to be practically unchanged in the ghosts from the erythrocytes treated at both pH values.

Effect of 2,3-diphosphoglycerate on the phosphorylation of protein 4.1 by protein kinase C

We have previously shown that 2,3-diphosphoglycerate (2,3-DPG) inhibits the phosphorylation of erythrocyte membrane cytoskeletal proteins by endogenous casein kinases. Here, we report that 2,3-DPG stimulates the phosphorylation of protein 4.1 by protein kinase C. Studies with red cell membrane preparations showed that while the phosphorylation of most of the membrane proteins by endogenous membrane-bound kinases and purified kinase C was inhibited by 2,3-DPG, the phosphorylation of protein 4.1 was slightly enhanced by the metabolite. The effect of 2,3-DPG was further examined using purified protein 4.1 preparations. Our results indicate that 2,3-DPG stimulates both the rate and the extent of phosphorylation of purified protein 4.1 by kinase C. The amount of phosphate incorporated was found to double to 2 mol of phosphate per mole of protein 4.1 in the presence of 10 mM 2,3-DPG. The increase in phosphorylation was distributed over all phosphorylation sites as revealed by an analysis of the labeling patterns of phosphopeptides resolved by high performance liquid chromatography, but a significantly higher incorporation was detected in two of the phosphopeptides. The stimulatory effect of 2,3-DPG on the phosphorylation of protein 4.1 was observed only with kinase C. Phosphorylation by the cytosolic erythrocyte casein kinase and the cyclic AMP-dependent protein kinase was inhibited by 2,3-DPG. Moreover, the stimulatory effect of 2,3-DPG seemed to be unique to the phosphorylation of protein 4.1 since a similar effect had not been observed with other protein kinase C substrates. Our results suggest that 2,3-DPG may play an important role in the regulation of cytoskeletal interactions.

Metabolic depletion effect on serine/threonine- and tyrosine-phosphorylations of membrane proteins in human erythrocytes

The response of serine/threonine-phosphorylation of the major transmembrane protein (band 3) in human erythrocytes to the metabolic state of the cells is different from that exhibited by the tyrosine-phosphorylation of the same protein. Precisely, both serine- and tyrosine-phosphorylation are decreased during metabolic depletion of the erythrocytes. However, the depletion-induced tyrosine-phosphorylation decrease of band 3 is not reversed by the subsequent metabolic repletion of the depleted cells, being accompanied by an irreversible inactivation of both membrane-bound and cytosolic tyrosine-protein kinase(s). By contrast, the depletion-induced phosphoserine-dephosphorylation is reversed by the following repletion, being accompanied by a reversible translocation of casein kinase(s) between cytosolic and membrane compartments. A possible functional correlation between the serine-phosphorylation state of band 3 protein and the band 3-mediated anion transport across the membrane is discussed.

Comparative characterization of membrane-associated and cytosolic Tyr-protein kinases in human erythrocytes

In recent years, two protein-tyrosine kinase activities, phosphorylating tyrosine residues on the transmembrane band-3 protein, have been isolated from human erythrocyte membranes and partially characterized by different laboratories, i.e. one extracted by non-ionic detergent (Triton X-100 or Nonidet P-40), the other solubilized by 0.25 M NaCl from the detergent-insoluble residue. The present paper shows that these two membrane-associated Tyr-protein kinases purified, in the presence of bovine serum albumin, by phosphocellulose chromatography followed by heparin-Sepharose chromatography, have the same apparent molecular mass (36 kDa) determined by Ultrogel Ac44 filtration. Moreover, both Tyr-protein kinases exhibit several identical properties, including Km values for band 3, the random acidic copolymer poly(Glu,Tyr)4:1 and angiotensin II, pH dependence, response to Mn2+ and Mg2+, response to NaCl and 2,3-bisphosphoglycerate. All these properties are identical or very similar to those exhibited by the Tyr-protein kinase previously isolated by us from human erythrocyte cytosol. These results suggest that the two membrane-associated and the cytosolic Tyr-protein kinase activities are mediated by the same enzyme, distributed between the cytosol and the membrane structures.

Interaction of hemoglobin with band 3: a review

The oxygen transport protein hemoglobin interacts specifically and reversibly with the red cell membrane. pH and ionic strength dependence of these interactions indicate their electrostatic nature. The anion transport protein band 3 has been implicated as the protein to which hemoglobin binds. Hemoglobin, aldolase and glyceraldehyde 3-phosphate dehydrogenase have a similar pH and ionic strength dependence in binding to 23K fragment. The three compete for the same amino-terminal 23 residue sequence region of band 3. The binding site is a highly acidic segment without any positive charge. We have recently determined the sequence of amino-terminal 23K fragment of band 3. There is a remarkable internal sequence homology between the first eleven and next eleven residues in this sequence region. Biophysical measurements in this sequence region. Biophysical measurements have revealed that 23K is a tetramer under physiological conditions. The implications of this structure of 23K is discussed with respect to the interaction of band 3 with the red cell cytoskeleton.