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Phosphorylation sequences in h‐caldesmon from phorbol ester‐stimulated canine aortas
Author(s) -
Adam Leonard P.,
Gapinski Connie J.,
Hathaway David R.
Publication year - 1992
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(92)80446-n
Subject(s) - caldesmon , phosphorylation , chemistry , phorbol , phorbol ester , protein kinase c , microbiology and biotechnology , biochemistry , calmodulin , biology , enzyme
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.