Phosphorylation sequences in h-caldesmon from phorbol ester-stimulated canine aortas.
The high molecular weight form of caldesmon (h-caldesmon) is phosphorylated in vascular smooth muscle. The stoichiometry of caldesmon phosphorylation increases in response to stimulation of the muscle by several contractile agonists; however, the responsible kinase has not been identified. In this study, we have sequenced the phosphopeptides prepared from h-caldesmon phosphorylated in vitro by protein kinase C (PKC) as well as the phosphopeptides prepared from caldesmon phosphorylated in intact canine aortas that were stimulated to contract with PDBu. PKC phosphorylated three sites located in the C terminus: GSS*LKIEE, AEFLNKS*VQK and NLWEKQS*VDK, while h-caldesmon from intact tissue was phosphorylated at two separate sites also in the C terminus: VTS*PTKV and S*PAPK. By comparison to known substrate consensus sequences for various protein kinases these data suggest that h-caldesmon is directly phosphorylated by a proline-directed protein kinase and not by PKC.
Adam
L P
LP
Department of Medicine, Indiana University School of Medicine, Indianapolis 46202.
Gapinski
C J
CJ
Hathaway
D R
DR
D000595:Amino Acid Sequence; D000818:Animals; D001011:Aorta / Q000737:chemistry / Q000187:drug effects; D001665:Binding Sites; D002148:Calmodulin-Binding Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D004285:Dogs; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009131:Muscle, Smooth, Vascular / Q000737:chemistry* / Q000187:drug effects; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology*; D010750:Phosphoproteins / Q000737:chemistry* / Q000378:metabolism; D010766:Phosphorylation; D038461:Proline-Directed Protein Kinases; D011493:Protein Kinase C / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism; D013552:Swine
D002148:Calmodulin-Binding Proteins; D010750:Phosphoproteins; D015240:Phorbol 12,13-Dibutyrate; D011494:Protein Kinases; D038461:Proline-Directed Protein Kinases; D011493:Protein Kinase C