Calmodulin in Skeletal Muscle

The central role of Ca2+ in the regulation of muscular activity is well documented. At the level of the contractile proteins the dominant effect of Ca2+ is attributable to the Ca2+-bindingprotein, troponin C. This protein in the presence of Ca2+ elicits conformational changes which allow cross-bridge cycling and hence contraction. Another Ca2+-binding protein, similar in its physical properties to troponin C, has also been discovered and this is calmodulin. The latter differs from troponin C in that it is involved in the regulation of a wide range of enzymatic reactions and it appears to be a ubiquitous regulatory protein. In skeletal muscle, as in all other eukaryotic cells, the number of calmodulin-dependent systems is too large to be considered and only two enzymes have been selected. These are myosin light chain kinase and phosphory lose kinase. The activities of both are intimately related to the contractile mechanism and for this reason their actions could be important to meat quality.