A 35-kilodalton fragment from gizzard smooth muscle caldesmon that induces F-actin bundles.
Specific thrombin proteolysis of native 120-kDa gizzard caldesmon gave rise to a major cleavage into an N-terminal 90-kDa and a C-terminal 35-kDa fragment. Fluorescent labeling, cosedimentation, passage through an affinity column, and carbodiimide crosslinking with actin revealed that the 35-kDa purified segment of the molecule contains the actin and the calcium-calmodulin binding regions. Electron microscopic analysis of its actin complex demonstrated that the 35-kDa segment possesses the bundling properties of the intact molecule. Thus, a possible pathway for the expression of the caldesmon regulatory function during smooth muscle contraction would be a conformational change twisting the helicoïdal structure of the actin filament, which occurs when the 35-kDa caldesmon portion binds to it.
Centre de Biochimie Macromoléculaire du CNRS, INSERM U 249, Université Montpellier I, France.
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Mornet
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Harricane
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Audemard
D000199:Actins / Q000032:analysis*; D000818:Animals; D002148:Calmodulin-Binding Proteins / Q000032:analysis*; D004591:Electrophoresis, Polyacrylamide Gel; D000070559:Gizzard, Non-avian / Q000032:analysis*; D008854:Microscopy, Electron; D008970:Molecular Weight
D000199:Actins; D002148:Calmodulin-Binding Proteins