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TYROSINE PHOSPHORYLATION OF CYTOSOLIC PROTEINS IN HUMAN ERYTHROCYTES
No full textSome cytosolic proteins of human erythrocytes can be phosphorylated on tyrosine residues by endogenous Tyr-protein kinase(s). Their phosphorylation is enhanced by addition of Tyr-protein kinase, purified from human erythrocyte cytosol. The most phosphorylatable is a 19 kDa protein. Its phosphorylation is more activated by Mn2+ than by Mg2+. It is inhibited by NaC1, 2,3-bisphosphoglycerate and by heparin. Similar response to the above effectors is exhibited by the phosphorylation of the other protein bands. However, the phosphorylation of a 73 kDa double band, which is negligible in the absence of added NaC1, is stimulated by this salt
Rat liver cytosol phosphoprotein: purification and enzymatic phosphorylation and dephosphorylation.
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DIDS-EFFECT ON SER THR-PHOSPHORYLATION AND TYR-PHOSPHORYLATION OF MEMBRANE-PROTEINS IN HUMAN ERYTHROCYTES
No full textBand 3, the major transmembrane multifunctional protein of human erythrocytes, has been found to be phosphorylated-dephosphorylated on both Ser/Thr- and Tyr-residues by specific protein kinases and protein phosphatases. The results reported here would indicate that the ghosts prepared from human erythrocytes pretreated with DIDS, well known inhibitor of band 3-mediated anion transport, exhibit a markedly reduced Ser/Thr-phosphorylation of spectrin and band 3, when incubated with [gamma-32P]ATP in the presence of Mg2+. On the other hand, Tyr-phosphorylation of this latter protein is practically unchanged or even slightly enhanced. This suggests that Ser/Thr- and Tyr-phosphorylation of band 3 display a different functional role
Comparative study of mitochondrial and cytosol protein kinase activities.
No full textBoth cytosol and mitochondria of rat liver display protein kinase activity, cyclic AMP-independent, which is resolved by Sepharose 6B filtration and P-cellulose chromatography into multiple forms phosphorylating, besides endogenous mitochondrial membrane-bound proteins, also exogenous phosphoproteins such as casein and phosvitin. However, the forms by far predominant in the cytosol phosphorylate both phosphorylserine and phosphorylthreonine residues of casein, while most of the activity associated to mitochondrial structures is due to the forms phosphorylating only phosphorylserine residues
Endogenous proteinkinase-dependent phosphorylation of rat liver mitochondrial membranes.
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