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The Journal of Physiology
Article . 2005 . Peer-reviewed
License: Wiley Online Library User Agreement
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Kinetics of muscle contraction and actomyosin NTP hydrolysis from rabbit using a series of metal–nucleotide substrates

Authors: Burton, K; White, H; Sleep, J;

Kinetics of muscle contraction and actomyosin NTP hydrolysis from rabbit using a series of metal–nucleotide substrates

Abstract

Mechanical properties of skinned single fibres from rabbit psoas muscle have been correlated with biochemical steps in the cross‐bridge cycle using a series of metal–nucleotide (Me·NTP) substrates (Mn2+ or Ni2+ substituted for Mg2+; CTP or ITP for ATP) and inorganic phosphate. Measurements were made of the rate of force redevelopment following (1) slack tests in which force recovery followed a period of unloaded shortening, or (2) ramp shortening at low load terminated by a rapid restretch. The form and rate of force recovery were described as the sum of two exponential functions. Actomyosin‐Subfragment 1 (acto‐S1) Me·NTPase activity and Me·NDP release were monitored under the same conditions as the fibre experiments. Mn·ATP and Mg·CTP both supported contraction well and maintained good striation order. Relative to Mg·ATP, they increased the rates and Me·NTPase activity of cross‐linked acto‐S1 and the fast component of a double‐exponential fit to force recovery by ∼50% and 10–35%, respectively, while shortening velocity was moderately reduced (by 20–30%). Phosphate also increased the rate of the fast component of force recovery. In contrast to Mn2+ and CTP, Ni·ATP and Mg·ITP did not support contraction well and caused striations to become disordered. The rates of force recovery and Me·NTPase activity were less than for Mg·ATP (by 40–80% and 50–85%, respectively), while shortening velocity was greatly reduced (by ∼80%). Dissociation of ADP from acto‐S1 was little affected by Ni2+, suggesting that Ni·ADP dissociation does not account for the large reduction in shortening velocity. The different effects of Ni2+ and Mn2+ were also observed during brief activations elicited by photolytic release of ATP. These results confirm that at least one rate‐limiting step is shared by acto‐S1 ATPase activity and force development. Our results are consistent with a dual rate‐limitation model in which the rate of force recovery is limited by both NTP cleavage and phosphate release, with their relative contributions and apparent rate constants influenced by an intervening rapid force‐generating transition.

Country
United Kingdom
Keywords

Male, 610, Models, Biological, Phosphates, Adenosine Triphosphate, Isometric Contraction, Animals, Computer Simulation, Muscle, Skeletal, Cells, Cultured, Muscle Cells, Nucleotides, Hydrolysis, 500, Actomyosin, 540, Elasticity, Kinetics, Energy Transfer, Metals, Rabbits, Stress, Mechanical

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    citations
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    24
    popularity
    This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
    Top 10%
    influence
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    Top 10%
    impulse
    This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
    Top 10%
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citations
This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Citations provided by BIP!
popularity
This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
BIP!Popularity provided by BIP!
influence
This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Influence provided by BIP!
impulse
This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
BIP!Impulse provided by BIP!
24
Top 10%
Top 10%
Top 10%
bronze
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