J. Biol. Chem., Vol. 268, Issue 29, 21901-21905, 10, 1993
Phosphorylation of dystrophin. The carboxyl-terminal region of dystrophin is a substrate for in vitro phosphorylation by p34cdc2 protein kinase
RE Milner, JL Busaan, CF Holmes, JH Wang and M Michalak
Cardiovascular Disease Research Group, University of Alberta, Edmonton, Canada.
In this paper, we report that p34cdc2 protein kinase phosphorylates
recombinant fragments of skeletal muscle dystrophin with a maximal
incorporation of 1.8 mol of Pi/mol of protein. Phosphorylation of both
serine and threonine residues occurs within the carboxyl-terminal 201 amino
acids of dystrophin, with phosphothreonine localized to within 25 residues
of the carboxyl terminus. Supporting these in vitro studies, we also show
that native dystrophin is phosphorylated by p34cdc2 kinase in isolated
sarcolemmal vesicles. Sequence analysis indicates two consensus sites for
p34cdc2 protein kinase within the carboxyl-terminal 201 amino acids of
dystrophin. Importantly, neither of these sites is conserved in
dystrophin-related protein, and only one site is conserved in the 71-kDa
alternative product of the Duchenne muscular dystrophy gene, despite an
otherwise extremely high degree of sequence conservation between these
proteins. Importantly, in this study we also show that dystrophin is
phosphorylated in vivo in rat skeletal muscle primary cultures, and we
suggest that further investigation of both in vivo and in vitro
phosphorylation of this protein will comprise an important part in
determination of its function(s).
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