Probing the Phosphorylation Theory in Triton Skinned Smooth Muscle

PROBING THE PHOSPHORYLATION THEORY IN TRITON SKINNED SMOOTH MUSCLE  

The fact that calmodulin diffuses out of triton skinned fibers could be used to demonstrate in recon- 

Using freeze-dried fibers, Riiegg and coworkers (1984) estimated the fraction of calmodulin available for activation of MLCK to be in the range of 0.3 to 4 yJVl, which is about 10% of the total cellular calmodulin. This pool is readily exchangeable and therefore rapidly equilibrates with the incubation medium (Riiegg et al., 1984). Similar results were obtained in triton skinned tracheal smooth muscle (Tansey et al., 1994). In contrast, calmodulin appears to be retained in P-escin-permeabilized tracheal smooth muscle (Tansey et al., 1994). 

Activation of Contraction by Phosphorylation of Myosin Light Chain 

Phosphorylation of MLC is generally accepted to be the primary event involved in the initiation of smooth muscle contraction (Kamm and Stull, 1985 Somlyo and Somlyo, 1994). In triton skinned taenia coli, phosphorylation and dephosphorylation of MLC preceded contraction and relaxation, respectively (Kiihn et al., 

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