The Lyn-catalyzed Tyr phosphorylation of the transmembrane band-3 protein of human erythrocytes.
Band-3 protein (approximately 95 kDa), the major and multifunctional transmembrane protein of human erythrocytes, has been shown to be phosphorylated by endogenous Tyr-protein kinases on different Tyr residues at its N and C cytoplasmic domains. Both the added p36syk (catalytic domain of p72syk) and Lyn kinases are able to phosphorylate the isolated cytoplasmic domain of band 3 (cdb3), yielded by chymotryptic digestion of band 3 in the isolated membranes (ghosts). However, the two Tyr-protein kinases exhibited different phosphorylation behaviours when added to the isolated erythrocyte membranes. More precisely, the added p36syk markedly Tyr phosphorylates the band-3 protein, whereas the added Lyn phosphorylates it very poorly. It is of interest that Lyn can associate with membranes and markedly phosphorylate band 3 when this latter protein has been previously phosphorylated by p36syk, i.e. the p36(syk)-catalyzed phosphorylation is proposed to be a prerequisite for the association of Lyn with the membrane (likely to band 3) and for the Lyn-catalyzed phosphorylation of different band-3 Tyr sites.
Brunati
A M
AM
Dipartimento di Chimica Biologica, Università di Padova, Italy.
Bordin
L
L
Clari
G
G
Moret
V
V
D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D001457:Anion Exchange Protein 1, Erythrocyte / Q000737:chemistry / Q000378:metabolism*; D015153:Blotting, Western; D002847:Chromatography, Agarose; D002855:Chromatography, Thin Layer; D004591:Electrophoresis, Polyacrylamide Gel; D004792:Enzyme Precursors / Q000378:metabolism; D004910:Erythrocyte Membrane / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D007700:Kinetics; D008565:Membrane Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D010449:Peptide Mapping; D010766:Phosphorylation; D011485:Protein Binding; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D000072377:Syk Kinase; D014443:Tyrosine / Q000378:metabolism*; D019061:src-Family Kinases / Q000378:metabolism*
D001457:Anion Exchange Protein 1, Erythrocyte; D004792:Enzyme Precursors; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D014443:Tyrosine; D000255:Adenosine Triphosphate; D011505:Protein-Tyrosine Kinases; C000606896:SYK protein, human; D000072377:Syk Kinase; C060902:lyn protein-tyrosine kinase; D019061:src-Family Kinases