Structure of a Calcium-Binding Carp Myogen

  1. Clive E. Nockolds†,*,
  2. Robert H. Kretsinger†,
  3. Carole J. Coffee‡, and
  4. Ralph A. Bradshaw‡
  1. †Department of Biology, University of Virginia, Charlottesville, Va. 22903
  2. ‡Department of Biological Chemistry, Washington University School of Medicine, St. Louis, Missouri 63110

Abstract

The amino-acid sequence and three-dimensional structure of a calcium-binding protein prepared from carp muscle has been determined. This protein, designated carp-muscle calcium-binding protein B, is one of three closely related parvalbumins found in this tissue. The electron density map, calculated by heavyatom substitution crystallographic methods to 2.0-Å resolution, reveals the orientation of most of the amino-acid side chains. The calcium coordination site consists of one glutamic- and three aspartic-acid carboxyl groups in a tetrahedral arrangement. The core of this spherical molecule is remarkably hydrophobic, with 8 of its 10 phenylalanine side chains packed in an approximate herringbone pattern. 52 of the 108 residues are in six α-helixes; there is no β-pleated sheet. The acetylated amino-terminal alanine appears not to be accessible to solvent. All of the heavy-atom derivatives are bound at the sole cysteine. The properties of this protein suggest a relationship to troponin A of mammalian tissue.

Footnotes

  • ↵ * Present address: Electron Microscopy Unit, University of Sydney, Sydney, Australia.

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  1. PNAS March 1, 1972 vol. 69 no. 3 581-584
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