Abstract
The role of caldesmon in the regulation of smooth muscle contraction was investigated in chemically skinned smooth muscle fibres from the guinea-pig taenia coli. A 19-kDa C-terminal fragment of caldesmon gave a minor (<5%) reduction of force in fully thiophosphorylated fibres, but reduced force by about 50% at intermediate activation levels without affecting the level of light chain phosphorylation. An extraction procedure was developed using incubation in solutions containing high Mg2+ concentrations. Protein analysis revealed a selective decrease in the amount of caldesmon in the fibres. Maximal active force per cross-sectional area was unaffected. The Ca2+ dependence of active force was shifted towards lower Ca2+ concentrations and became less steep. The effects of extraction of caldesmon could in part be reversed by incubation in a solution containing purified caldesmon. The results are consistent with the hypothesis that caldesmon in smooth muscle thin filaments inhibits force generation and plays a role in regulating cooperative attachment of cross-bridges at sub-maximal levels of activation in smooth muscle.
Original language | English |
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Pages (from-to) | 241-247 |
Journal | Pflügers Archiv |
Volume | 432 |
Issue number | 2 |
DOIs | |
Publication status | Published - 1996 |
Subject classification (UKÄ)
- Pharmacology and Toxicology
- Medicinal Chemistry
Keywords
- Skinned smooth muscle
- Caldesmon
- 19-kDa fragment
- Calcium sensitivity