Abstract
Crude actin extracts from acetone-dried powder of the muscle layer of bovine aorta contain an actin-modulating protein which promotes nucleation of actin monomers and decreases the average length of actin filaments in a Ca 2+-dependent manner. This observation has allowed the development of an improved purification procedure for aorta actin which increases the yield 2- to 3-times. The actin obtained with this procedure consists of 77% α- and 23% γ-isoelectric species. Pure aorta actin is indistinguishable from actins from skeletal, cardiac and chicken-gizzard smooth muscle in its polymerization rate, critical concentration, and reduced viscosity when polymerized with KCl at 25°C. It differs from sarcomeric actins, but not from chicken-gizzard smooth muscle actin, in the temperature dependence of polymerization equilibria in KCl. This difference correlates with the amino acid replacements Val-17 → Cys-17 and Thr-89 → Ser-89, supporting a conclusion drawn from other studies that the N-terminal portion of actin polypeptide chain contains sites important for polymerization.
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Schedule a callMore From: Biochimica et Biophysica Acta (BBA) - Protein Structure and Molecular Enzymology
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