Flash photolysis studies of relaxation and cross-bridge detachment: higher sensitivity of tonic than phasic smooth muscle to MgADP

@article{Fuglasang2004FlashPS,
  title={Flash photolysis studies of relaxation and cross-bridge detachment: higher sensitivity of tonic than phasic smooth muscle to MgADP},
  author={Annette Fuglasang and A. Khromov and K. T{\"o}r{\"o}k and A. Somlyo},
  journal={Journal of Muscle Research \& Cell Motility},
  year={2004},
  volume={14},
  pages={666-677}
}
SummaryThe effects of MgADP and inorganic phosphate (Pi) on cross-bridge detachment were determined in tonic (rabbit femoral artery) and phasic (rabbit bladder and guinea pig portal vein) smooth muscles permeabilized with staphylococcal α-toxin. Relaxation from rigor was induced by photolysis of ATP (1.2–1.5 mm) from caged ATP. The initial one second of relaxation from rigor was resolved into two exponential components: a rapid component with normalized amplitudes, Af, of 8, 15 and 26% and rate… Expand
Smooth muscle myosin: regulation and properties.
  • A. Somlyo, A. Khromov, +6 authors A. Somlyo
  • Chemistry, Medicine
  • Philosophical transactions of the Royal Society of London. Series B, Biological sciences
  • 2004
TLDR
ADP release in phasic and tonic smooth muscles is a regulated step with strain- and dephosphorylation-dependence and may limit the ATPase rate, according to the rates of ADP release from rigor cross-bridges and the steady-state Pi release from cycling isometric cross- bridges. Expand
Myosin regulatory light chain phosphorylation and strain modulate adenosine diphosphate release from smooth muscle Myosin.
TLDR
It is concluded that the strain- and dephosphorylation-dependent high affinity for and slow ADP release from smooth muscle myosin prolongs the fraction of the duty cycle occupied by strongly bound actomyosin and contributes to the high economy of force. Expand
Affinity for MgADP and force of unbinding from actin of myosin purified from tonic and phasic smooth muscle.
TLDR
The greater affinity for MgADP of tonic muscle myosin and the reattachment of dephosphorylated myOSin to actin may both contribute to the latch state. Expand
The Unique Properties of Tonic Smooth Muscle Emerge from Intrinsic as Well as Intermolecular Behaviors of Myosin Molecules*
TLDR
It is shown that the relatively slow actin velocity generated by minus-insert heavy meromyosin is significantly influenced, but not limited, by k–D, which supports a model in which two separate intermediate steps in the actin-myosin catalyzed ATP hydrolysis reaction are energetically coupled through mechanical interactions. Expand
Regulation of catch muscle by twitchin phosphorylation: effects on force, ATPase, and shortening.
TLDR
The data suggest that during both catch and calcium-mediated submaximum contractions, twitchin phosphorylation removes a structure that maintains force with a very low ATPase, but which can slowly cycle during submaximum calcium activation. Expand
Nonmuscle myosin, force maintenance, and the tonic contractile phenotype in smooth muscle
TLDR
The results suggest that NM myosin contributes to the mechanism of force maintenance in smooth muscle, and could suggest that the expression of NMIIB is a factor for determining the tonic contractile phenotype. Expand
Inhibition of oxidative phosphorylation, vascular tone, and [Ca2+]i in the perfused rat tail artery.
TLDR
Investigation of the possibility that the inhibition of oxidative phosphorylation in vascular smooth muscle attenuates norepinephrine- or KCl-evoked vasoconstriction with no change in mobilization of intracellular calcium concentration suggests that [Ca2+]i homeostasis can be maintained in the presence of inhibitors of oxidativeosphorylation. Expand
Creatine kinase activity associated with the contractile proteins of the guinea-pig carotid artery
TLDR
The results suggest co-localization of ATPase, MLCK, and creatine kinase on the contractile proteins of the carotid artery may play a role in the energetic supply to thecontractile apparatus of vascular smooth muscle. Expand
Evidence for absence of latch-bridge formation in muscular saphenous arteries.
TLDR
Data support the hypothesis that maintained isometric force was 40% less in SA than in FA because expressed motor proteins in SA do not support latch-bridge formation, and correlated with reduced myosin light chain phosphorylation in SA. Expand
Ablation of smooth muscle caldesmon affects the relaxation kinetics of arterial muscle
TLDR
The finding that h-CaD modulates the rate of smooth muscle relaxation clearly supports a role in the control of vascular tone and is proposed to reflect a thin filament state that elicits fewer re-attached crossbridges. Expand
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