A novel 550-kDa protein in skeletal muscle of chick embryo: purification and localization

Abstract

We have found a novel protein with a molecular mass of 550 kDa on SDS-polyacrylamide gels, which is abundant in skeletal muscle tissues at an early stage of chick embryonic development. The 550-kDa protein decreased with the progress of development, and only a slight amount of the protein was present in adult chicken skeletal muscle. The 550-kDa protein was purified from the cytoplasm of 18 day embryos by a procedure including ultracentrifugation and gel filtration. The purified 550-kDa protein was essentially free of contaminants as judged by SDS-PAGE. By immunofluorescence and immunoelectron microscopy using the antibody raised against the 550-kDa protein, this protein was shown to be localized in the peripheries of adult muscle fibers and at the Z-disks of isolated myofibrils. These findings have led us to conclude that the 550-kDa protein is a novel myofibrillar protein in chicken skeletal muscle.