Key result
Smooth muscle calponin binding to actin filaments causes delayed intrinsic conformational changes in actin that are not correlated with actin filament bundling.
Ratio-dependent calponin-F-actin bundling may affect smooth muscle tone; leaves open any role in vascular disease.
Kinetics of the smooth muscle calponin-F-actin interaction was studied by stopped-flow measurements of light scattering and fluorescence intensity of pyrene-labelled F-actin. The intensity and character of the changes in light scattering, and thus the mode of calponin binding to actin filaments leading to changes in their shape and bundling, depend on the molar ratio of the two proteins. Parallel measurements of pyrene-fluorescence quenching upon calponin binding revealed that intrinsic conformational changes in actin filaments are delayed relative to the binding process and are not markedly influenced by the mode of calponin binding. Bundling of actin filaments by calponin was not correlated with fluorescence changes and thus with alterations in the structure of actin filaments.
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Kołakowski et al. (2002) studied this question. Smooth muscle calponin was evaluated on Kinetics and mode of calponin-F-actin interaction. Smooth muscle calponin binding to actin filaments causes delayed intrinsic conformational changes in actin that are not correlated with actin filament bundling.
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