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Titolo:
SMOOTH-MUSCLE CALDESMON CONTROLS THE STRONG BINDING INTERACTION BETWEEN ACTIN-TROPOMYOSIN AND MYOSIN
Autore:
MARSTON SB; FRASER IDC; HUBER PAJ;
Indirizzi:
NATL HEART & LUNG INST,DEPT CARDIAC MED,DOVEHOUSE ST LONDON SW3 6LY ENGLAND
Titolo Testata:
The Journal of biological chemistry
fascicolo: 51, volume: 269, anno: 1994,
pagine: 32104 - 32109
SICI:
0021-9258(1994)269:51<32104:SCCTSB>2.0.ZU;2-Y
Fonte:
ISI
Lingua:
ENG
Soggetto:
ACTOMYOSIN SUBFRAGMENT-1 ATPASE; THIN-FILAMENTS; TROPONIN-TROPOMYOSIN; HEAVY-MEROMYOSIN; COOPERATIVE BINDING; CALMODULIN-BINDING; REGULATED ACTIN; SKELETAL; COMPLEX; DISSOCIATION;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
55
Recensione:
Indirizzi per estratti:
Citazione:
S.B. Marston et al., "SMOOTH-MUSCLE CALDESMON CONTROLS THE STRONG BINDING INTERACTION BETWEEN ACTIN-TROPOMYOSIN AND MYOSIN", The Journal of biological chemistry, 269(51), 1994, pp. 32104-32109

Abstract

We have demonstrated that caldesmon does not alter the affinity of weak binding actomyosin complexes when it inhibits actin-tropomyosin activation at physiological ratios (1 per 14 actins), and we proposed that it acts upon the strong binding complexes in the same way that troponin-tropomyosin does. We therefore compared the effect of caldesmon, caldesmon fragments, and troponin upon the interaction of the strongly bound complexes S-1 ADP, S-1 adenylyl imidodiphosphate (AMP-PNP), and N-ethylmaleimide-treated myosin subfragment-1 (NEM-S1) with actin-tropomyosin. In 0.17 M ionic strength buffer [C-14]iodoacetamide-labeled S1-ADP bound to actin-smooth muscle tropomyosin with no evidence of cooperativity; K-d = 0.8 +/- 0.3 mu M (n = 5). Inhibitory concentrations of sheep aorta caldesmon or rabbit skeletal muscle troponin made the binding highly cooperative. At low levels of saturation the apparent K-d was 10-40 mu M with 10 mu M caldesmon and 8-20 mu M with 6 mu M troponin; at > 50% saturation the binding was indistinguishable from actin-tropomyosin alone. A similar result was obtained for the binding of [C-14]iodoacetamide-labeled S-1.AMP.PNP to actin-smooth muscle tropomyosin at 0.03 M ionic strength (K-d = 0.47 +/- 0.05 mu M). Binding was slightly cooperative and became highly cooperative in the presence of inhibitory concentrations of troponin, caldesmon, and the human caldesmon fragments H7 (amino acids 622-767) and H9 (amino acids 726-793). Weconclude that caldesmon and troponin both act as allosteric effectersof the ''on''/''off'' equilibrium of actin-tropomyosin. 0.1 NEM-S-1/actin potentiated actin-smooth muscle tropomyosin activation of myosin MgATPase 7-fold at 0.03 M ionic strength. Caldesmon inhibited the ATPase in the presence and absence of 0.5 mu M NEM-S-1. NEM-S-1 reactivated actin-tropomyosin, which had been inhibited by troponin, caldesmon, H7, or H9. This is compatible with opposing effects of NEM-S-1 and caldesmon or troponin upon the actin-tropomyosin on/off equilibrium.

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Documento generato il 19/09/20 alle ore 09:13:47