A monovalent cation-sensitive actin-binding factor in a myeloid leukemia cell line.

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Cell extracts of a murine leukemia cell line, Ml, apparently contain three kinds of actin-gelation factors; a filamin-like protein, and 38Kdimer and 105K-dimer proteins. Unlike gelation by the filamin-like protein, gelation by the latter two proteins is inhibited by low concentrations of KCl. Our study of the 38K protein has been reported elsewhere (Takagi, K. et al., J. Biochem. Tokyo 97, 605-616, 1985). We here describe the purification and characterization of the 105K protein.<BR>The 105K protein differs from the a-actinin group of proteins in its antigenicity, peptide components and Ca<SUP>2+</SUP>-insensitivity. The saturated binding ratio of the protein to purified skeletal muscle actin is 1 : 8; when this ratio exceeds 1 : 20, gelation takes place. This gelation is inhibited completely by the presence of 25 mM KC1. Electron microscopy revealed that, in the absence of KC1, the 105K protein/actin mixture forms short actin bundles that are accompanied by a meshwork of short single filaments. The presence of 25 mM KC1 did not prevent actin-bundling, but the bundles became longer and the meshwork of short filaments was no longer present.
日本細胞生物学会の論文