A calponin peptide enhances Ca2+ sensitivity of smooth muscle contraction without affecting myosin light chain phosphorylation.
In permeabilized smooth muscle, exogenously applied calponin binds to myofibrils and reduces Ca(2+)-activated tension (Itoh, T., Suzuki, S., Suzuki, A., Nakamura, F., Naka, M., and Tanaka, T. (1994) Pflügers Arch. Eur. J. Physiol. 427, 301-308). A calponin peptide (calponin Phe173-Arg185), which inhibits the binding of calponin to actin, blocks the action of calponin and enhances the contraction induced by submaximal Ca2+ in permeabilized vascular smooth muscle. Unlike calmodulin, this peptide enhances the Ca(2+)-induced contraction without a corresponding increase in the level of myosin light chain phosphorylation. These results suggest that calponin decreases the sensitivity of smooth muscle to Ca2+ at a given level of myosin light chain phosphorylation.
Itoh
T
T
Department of Pharmacology, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
Suzuki
A
A
Watanabe
Y
Y
Mino
T
T
Naka
M
M
Tanaka
T
T
D000199:Actins / Q000302:isolation & purification / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D001921:Brain / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000737:chemistry / Q000494:pharmacology*; D002147:Calmodulin / Q000302:isolation & purification / Q000494:pharmacology; D002645:Chickens; D005895:Gizzard, Avian; D007700:Kinetics; D008840:Microfilament Proteins; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D009124:Muscle Proteins / Q000494:pharmacology; D018482:Muscle, Skeletal / Q000378:metabolism; D009130:Muscle, Smooth / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology*; D009218:Myosins / Q000378:metabolism*; D010446:Peptide Fragments / Q000737:chemistry / Q000494:pharmacology*; D010766:Phosphorylation; D011817:Rabbits; D000096985:Calponins
D000199:Actins; D002118:Calcium; D002135:Calcium-Binding Proteins; D002147:Calmodulin; D008840:Microfilament Proteins; D009124:Muscle Proteins; D009218:Myosins; D010446:Peptide Fragments; D000096985:Calponins