Nebulin

Literature References: Family of giant, actin-binding proteins, varying in size from 700-900 kDa, found in the sarcomeres of vertebrate skeletal muscles; comprises ~3% of the total myofibrillar protein. Composed of small repeats of ~35 amino acid residues arranged in a 7-fold super-repeating pattern. Integral component of the cytoskeletal lattice of muscle cells (see also Titin). Forms inextensible filaments that are attached to the Z-line and span the length of the thin filaments. Thought to act as a "molecular ruler" that stabilizes the actin polymer and regulates thin filament length. Name derived from its histological localization in the N2-line of the sarcomere, a nebulous striation within the I-band. Identification: K. Wang, C. L. Williamson, Proc. Natl. Acad. Sci. USA 77, 3254 (1980). Distribution and organization in cytoskeletal matrix of striated muscle: K. Wang, Adv. Exp. Med. Biol. 170, 285-305 (1984). Physiological role: M.-J. G. Chen et al., J. Biol. Chem. 268, 20327 (1993). Quantitative determn by gel electrophoresis: H. L. M. Granzier, K. Wang, Electrophoresis 14, 56 (1993). Structural study: M. Pfuhl et al., EMBO J. 13, 1782 (1994). Complete primary structure: S. Labeit, B. Kolmerer, J. Mol. Biol. 248, 308 (1995). Review: J. Trinick, Trends Biochem. Sci. 19, 405-409 (1994).