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TABLE I

Concentrations of Myoplasmic Constituents in Mouse EDL Fibers

1
2
3
Constituent
Concentration (μM)
Concentration of binding
 sites (μM)
resting [Ca2+0.050 – 
resting [Mg2+1,000 – 
troponin 120 240 (Ca2+ regulatory sites) 
SR Ca2+ pump 120 240 (Ca2+ transport sites) 
parvalbumin 750 1,500 (Ca2+/Mg2+ sites) 
ATP 8,000 8,000 (Ca2+/Mg2+ sites) 
furaptra 100 100 (Ca2+/Mg2+ sites) 
protein 500 500 (furaptra sites) 
1
2
3
Constituent
Concentration (μM)
Concentration of binding
 sites (μM)
resting [Ca2+0.050 – 
resting [Mg2+1,000 – 
troponin 120 240 (Ca2+ regulatory sites) 
SR Ca2+ pump 120 240 (Ca2+ transport sites) 
parvalbumin 750 1,500 (Ca2+/Mg2+ sites) 
ATP 8,000 8,000 (Ca2+/Mg2+ sites) 
furaptra 100 100 (Ca2+/Mg2+ sites) 
protein 500 500 (furaptra sites) 

Concentrations are spatially averaged and referred to the myoplasmic water volume (Baylor et al., 1983); except for free [Ca2+] and free [Mg2+], total concentrations are given. Except for furaptra and protein, the values assumed here for EDL fibers are the same as those given by Hollingworth et al. (2006) for frog twitch fibers. The furaptra and protein concentrations apply to Fig. 2 E and Table II (E). pH is assumed to be 7 and constant.

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