Functional link between phosphorylation state of membrane proteins and morphological changes of human erythrocytes

The Tyr-phosphorylation of the cytoplasmic domain of the major membrane-spanning band 3, rather than the Ser/Thr-phosphorylation of the membrane proteins (spectrin and band 3 itself), might be functionally related to certain morphological changes of human erythrocytes. This view is supported by the following lines of evidence: a) vanadate or its derivative pervanadate (vanadyl hydroperoxide), which markedly increase the Tyr-phosphorylation of band 3 (without practically affecting the Ser/Thr-phosphorylation of spectrin) promotes a crenation of human erythrocytes; b) okadaic acid, which selectively increases the Ser/Thr-phosphorylation of spectrin and other membrane proteins, does not promote any shape change, at least at a level detectable with scanning electron microscopy.