Phosphorylation of high-Mr caldesmon by protein kinase C modulates the regulatory function of this protein on the interaction between actin and myosin.
High-Mr caldesmon, which is involved in smooth muscle contraction, was phosphorylated by protein kinase C. By chymotryptic digestion, actin- and calmodulin-binding assays and immunoprecipitation with the antibody to the C-terminal 35-kDa fragment, we have identified that all phosphate groups are incorporated exclusively into this fragment, which is the functional domain for binding actin and calmodulin. Phosphorylation of high-Mr caldesmon and its C-terminal 35-kDa fragment reduced their binding abilities to both F-actin and calmodulin. Further, their inhibitory effects on the actin-activated ATPase activity of gizzard myosin were also reversed in proportion to the degree of phosphorylation. These results suggest that phosphorylation of high-Mr caldesmon by protein kinase C, which is restricted within the C-terminal 35-kDa domain, results in the modulation of its activity in the smooth muscle actin--myosin interaction.
Tanaka
T
T
Department of Neuropharmacology and Neurochemistry, Osaka University Medical School, Japan.
Ohta
H
H
Kanda
K
K
Tanaka
T
T
Hidaka
H
H
Sobue
K
K
D000199:Actins / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D001665:Binding Sites / Q000187:drug effects; D002147:Calmodulin / Q000378:metabolism / Q000494:pharmacology; D002148:Calmodulin-Binding Proteins / Q000378:metabolism* / Q000494:pharmacology / Q000502:physiology; D002645:Chickens; D002918:Chymotrypsin / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D005895:Gizzard, Avian; D009218:Myosins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010748:Phosphopeptides / Q000032:analysis; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D014335:Tropomyosin / Q000494:pharmacology
D000199:Actins; D002147:Calmodulin; D002148:Calmodulin-Binding Proteins; D010748:Phosphopeptides; D014335:Tropomyosin; D011493:Protein Kinase C; D002918:Chymotrypsin; D009218:Myosins