pIClnand Cytosolic F-Actin Constitute a Heteromeric Complex with a Constant Molecular Mass in Rat Skeletal Muscles1.

To elucidate the function of pIC1n, its localization in subcellular organellae was investigated. A specific polyclonal anti-pIC1n antibody detected the soluble 38-kDa plC1n exclusively in the cytosols of rat heart, lung, liver, spleen, skeletal muscle, testis, and brain, but not rat kidney, plC1n -associated proteins in skeletal muscle were also analyzed. Native-gradient PAGE showed a single 340-kDa protein band reactive to anti-pIC1n antibody. This band also stained with anti-actin antibody. Two-dimensional PAGE and immunoprecipitation analysis indicated that all of the pIC1n was present in association with actin of a constant length: the molecular ratio of plcm to actin was roughly 1: 7. In addition, all actin in the cytosol fractions was found in association with pIC1n- These results suggest the possibility that skeletal muscle plC1n controls the length of cytosolic F-actin. [ABSTRACT FROM AUTHOR]