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JBC, Vol. 252, Issue 1, 102-109, Jan, 1977
M. M. Hosey and M. Tao
Previous reports from this laboratory and others have established that both
the rabbit and human erythrocyte membranes contain multiple protein kinase
and phosphate acceptor activities. We now report that these membranes also
contain phosphoryl acceptor sites for the soluble cyclic AMP-dependent and
-independent protein kinases from rabbit erythrocytes. The rabbit
erythrocyte membrane, which does not contain a cyclic AMP-dependent protein
kinase, has at least four polypeptides (Bands 2.1, 2.3, 4.5, and 4.8) which
are phosphorylated in the presence of the soluble cyclic AMP-dependent
protein kinases I, IIa, and IIb isolated from rabbit erythrocyte lysates.
The resulting phosphoprotein profile is very similar to that obtained for
the cyclic AMP-mediated autophosphorylation of human erythrocyte membranes.
The activities of the soluble cyclic AMP-dependent protein kinases toward
the membranes have been studied at several pH values. Although the
substrate specificity of the three kinases is similar, polypeptide 2.3
appears to be phosphorylated to a greater extent by kinase IIa than by I or
IIb. This occurs at all pH values studied. Also apparent is that the pH
profile for membrane phosphorylation is different from that of histone
phosphorylation. The phosphorylation of membrane proteins can also be
catalyzed by the soluble erythrocyte casein kinases. These enzymes are not
regulated by cyclic nucleotides and can use either ATP or GTP as their
phosphoryl donor. Polypeptides 2.1, 2.9, 4.1, 4.5, 4.8, and 5 of both human
and rabbit erythrocyte membranes are phosphorylated in the presence of GTP
and the casein kinases. This reaction is optimal at pH 7.5. Experiments
were performed to determine whether the phosphorylation of the membranes by
the soluble and membrane-bound kinases is additive or exclusive. Our
results indicate that after maximal autophosphorylation of the erythrocyte
membranes, phosphoryl acceptor sites are available to the soluble cyclic
AMP-dependent and -independent protein kinases. Furthermore, after maximal
phosphorylation of the membranes with one type of soluble kinase, further
32P incorporation can occur as a result of exposure to the other type of
soluble kinase.
Phosphorylation of rabbit and human erythrocyte membranes by soluble adenosine 3':5'-monophosphate-dependent and -independent protein kinases
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