Caldesmon is an elongated, flexible molecule localized in the actomyosin domains of smooth muscle.
A rapid purification procedure has been developed for the isolation of caldesmon from hog stomach smooth muscle utilizing a KI extract of washed myofibrils as source material. On SDS-PAGE this mammalian caldesmon showed a closely-spaced doublet around 155 kd. By low-angle rotary shadowing caldesmon was shown to be an elongated, highly flexible molecule which tends to form end-to-end dimers that are structurally very similar to filamin. When added to F-actin solutions caldesmon increased the high-shear viscosity considerably, but by an extent that depended on sample preparation. The effect was shown to be due to caldesmon and not to a trace contaminant by its full reversibility after addition of a monospecific caldesmon antibody. Recent investigations have shown that in smooth muscle two structurally distinct domains can be distinguished: an actomyosin domain and an actin-intermediate filament domain. Immunocytochemistry of ultrathin sections of smooth muscle at the light and electron microscope level revealed that caldesmon is present in the actomyosin domain. Caldesmon is thus a potential regulator of the actomyosin system in smooth muscle.
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Fürst
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De Mey
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Small
D000199:Actins / Q000378:metabolism; D000205:Actomyosin / Q000302:isolation & purification*; D000818:Animals; D000906:Antibodies; D000936:Antigen-Antibody Complex; D002148:Calmodulin-Binding Proteins / Q000302:isolation & purification* / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D008854:Microscopy, Electron; D009130:Muscle, Smooth / Q000032:analysis*; D009210:Myofibrils / Q000032:analysis*; D011487:Protein Conformation; D013270:Stomach / Q000032:analysis; D013552:Swine; D014783:Viscosity
D000199:Actins; D000906:Antibodies; D000936:Antigen-Antibody Complex; D002148:Calmodulin-Binding Proteins; D000205:Actomyosin