β-actinin

A capping protein at the pointed end of thin filaments in skeletal muscle

Takashi Funatsu, Yoko Asami, Shin'ichi Ishiwata

    Research output: Contribution to journalArticle

    13 Citations (Scopus)

    Abstract

    We examined the function of β-actinin as a pointed end capping protein of thin filaments in skeletal muscle. An improvement in preparing β-actinin yielded purified β-actinin which retained its activity for more than a week. Two-dimensional gel electrophoresis showed that the two subunits, βI and βII of β-actinin are, respectively, split into two to three components (isoforms) with different isoelectric points. Polyclonal antibody was raised by injecting such purified and undenatured chicken breast muscle β-actinin composed of several components into a rabbit. Immuno-gold labeling examination with electron microscopy of an F-actin-β-actinin complex, decorated with HMM showed that 85% of bound gold particles was on the pointed end of actin filaments, while the remaining 15% was on the barbed end. This suggests that in β-actinin preparation pointed end and barbed end capping proteins inevitably coexist. Immunofluorescence and immunoelectron microscopy directly showed that-actinin is located at the pointed end of thin filaments in myofibrils; it was also suggested that a capping protein having common antigenic determinants to β-actinin is located at Z-line. Thus, the physiological function of β-actinin as a pointed end capping protein was examined as follows: When β-actinin was dissociated from the pointed end of thin filaments in an I-Z-I brush by using a high salt solution, thin filaments could be disassembled at the pointed ends at concentrations of exogenous actin lower than a critical value. At a physiological ionic strength, these salt-washed thin filaments gradually shortened at a constant rate of about 45 nm/h. Both the association and dissociation of monomeric actin at the pointed end were suppressed by the rebinding of exogenous β-actinin. The main physiological role of β-actin in is therefore to stabilize thin filaments in the sarcomere by preventing addition and removal of actin monomers at the pointed filament end.

    Original languageEnglish
    Pages (from-to)61-71
    Number of pages11
    JournalJournal of Biochemistry
    Volume103
    Issue number1
    Publication statusPublished - 1988 Jan

    Fingerprint

    Actinin
    Skeletal muscle
    Filament
    Muscle
    Actin
    Skeletal Muscle
    Proteins
    Protein
    Actins
    Gold
    Salts
    Brushes
    Ionic strength
    Electrophoresis
    Antibodies
    Salt
    Labeling
    Electron microscopy
    Microscopic examination
    Gels

    ASJC Scopus subject areas

    • Statistics, Probability and Uncertainty
    • Applied Mathematics
    • Physiology (medical)
    • Radiology Nuclear Medicine and imaging
    • Molecular Biology
    • Biochemistry

    Cite this

    β-actinin : A capping protein at the pointed end of thin filaments in skeletal muscle. / Funatsu, Takashi; Asami, Yoko; Ishiwata, Shin'ichi.

    In: Journal of Biochemistry, Vol. 103, No. 1, 01.1988, p. 61-71.

    Research output: Contribution to journalArticle

    Funatsu, T, Asami, Y & Ishiwata, S 1988, 'β-actinin: A capping protein at the pointed end of thin filaments in skeletal muscle', Journal of Biochemistry, vol. 103, no. 1, pp. 61-71.
    Funatsu, Takashi ; Asami, Yoko ; Ishiwata, Shin'ichi. / β-actinin : A capping protein at the pointed end of thin filaments in skeletal muscle. In: Journal of Biochemistry. 1988 ; Vol. 103, No. 1. pp. 61-71.
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