cAMP-dependent protein kinase rapidly phosphorylates serine- 687 of the skeletal muscle receptor for calcium channel blockers.
The cAMP-dependent phosphorylation of the 165-kDa subunit of the receptor for organic calcium channel blockers (CaCB-receptors) was studied. Tryptic peptide analysis showed that cAMP-dependent protein kinase phosphorylates rapidly a serine in one peptide. Up to three peptides containing phosphoserine and -threonine are phosphorylated in a 2-h incubation. The isolated 165-kDa subunit was digested with trypsin and the endoproteinase Lys-C and Glu-C. The rapidly phosphorylated peptide was isolated from each digest. The amino acid sequence was determined by Edman degradation and compared with the deduced amino acid sequence of the CaCB-receptor from rabbit skeletal muscle (Tanabe, T., Takeshima, H., Mikami, A., Flockerzi, V., Takahashi, H., Kangawa, K., Kojima, M., Matsuo, H., Hirose, T., and Numa, S. (1987) Nature 238, 313-318). Phosphoserine was determined as the phenylthiohydantoin-derivative of dithiothreitol-dehydroalanine. The phosphorylated serine was identified as Ser-687 which is localized between the transmembrane regions II and III. A second phosphopeptide was isolated into which phosphate was incorporated into Ser-1617 with a slow time course. This peptide is located in the COOH-terminal cytoplasmic domain of the 165-kDa subunit. It is anticipated that phosphorylation of serine 687 affects the opening probability of the calcium channel.
Röhrkasten
A
A
Institut für Physiologische Chemie, Medizinische Fakultät, Universität des Saarlandes, Homburg/Saar, Germany.
Meyer
H E
HE
Nastainczyk
W
W
Sieber
M
M
Hofmann
F
F
D000818:Animals; D015220:Calcium Channels; D008970:Molecular Weight; D009132:Muscles / Q000378:metabolism; D010449:Peptide Mapping; D010766:Phosphorylation; D010768:Phosphoserine / Q000032:analysis; D011494:Protein Kinases / Q000378:metabolism*; D011817:Rabbits; D011978:Receptors, Nicotinic / Q000378:metabolism*; D012694:Serine / Q000378:metabolism*
D015220:Calcium Channels; D011978:Receptors, Nicotinic; D010768:Phosphoserine; D012694:Serine; D011494:Protein Kinases