Two Forms of Chicken Gizzard F-Actin Depending on Preparation with or without Added Calcium

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Abstract
Actin was obtained in high purity and with a high yield from acetone powder of fresh chicken gizzard muscle without pre-extraction of myosin. 1. The gizzard acting migrated as a single band in SDS-gel electrophoresis, showing a molecular weight of 42, 000±1, 000. The amino acid composition of gizzard actin was almost identical with those of utrine and skeletal actins. Gizzard actin contained approximately 6 cysteinyl residues per mol of actin whereas skeletal actin contained 5 cysteinyl residues per mol. 2. Two forms of F-actin, 83S and 36S, were obtained depending on whether or not calcium ions were present in the medium used for extraction and depolymerization. 83S F-actin was similar to skeletal F-actin in viscosity, sedimentation coefficient and the degree of activation of myosin-Mg2+-ATPase activity. 36S F-actin solution showed extremely low viscosity, steady ATP splitting, and slightly activated myosin ATPase. 3. When dialyzed against a buffer without added calcium, gizzard G-actin, which was otherwise capable of polymerizing to 83S F-actin, was transformed to 36S-forming G-actin with concomitant loss of a considerable amount of calcium.

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