S.J.C. thanks the BBSRC for a graduate studentship.
University of Heidelberg (2006) Proc Physiol Soc 4, PC1
Poster Communications: Gerald F. Elliott1, Susan J. Coomber2
1. Nuffield Laboratory of Ophthalmology, Oxford, United Kingdom. 2. Lodge Park Technolgy College, Corby , Northants, United Kingdom.
In a communication to the European Muscle Congress (2006) meeting Elliott & Worthington [1] set out the very strong experimental evidence from biochemistry and physiology suggesting that cross-bridges act sequentially (rather than simultaneously) along a given actin filament during the contraction of striated muscle. Here we suggest how sequential operation is initiated and controlled. In glycerinated muscle (psoas from rabbits killed by approved procedures) Coomber et al. [2,3] used Donnan potential measurements with KCl-filled microelectrodes to show that the electric charge on the actin-myosin matrix undergoes a sharp switch-like transition at pCa 50 = 6.2. The potentials are about 2 mV less negative at the lower pCa (P 4.3 μm) abolished the dependence. These experiments suggest very strongly that the calcium dependence is controlled by the titin component of the sarcomere, and is lost when titin filaments break. There is now renewed interest in the electric charge of those proteins in muscle within the structural system; here we suggest how changes in these charges may control the calcium activation process.
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