Characterization of Cardiac Calsequestrin

Biochemistry. 1987 Oct 6;26(20):6539-44. doi: 10.1021/bi00394a038.

Abstract

Calsequestrin, a calcium-binding protein found in the sarcoplasmic reticulum of muscle cells, was purified from rabbit and canine cardiac and skeletal muscle tissue. The amino acid compositions and amino-terminal sequences of skeletal and cardiac calsequestrin from rabbit and dog were determined. The amino acid composition of the cardiac form was very similar to the skeletal form. The amino-terminal sequence of the cardiac form was homologous to, but not identical with, the amino-terminal sequence of the skeletal form of the protein. Few species differences in the amino-terminal sequences were observed. The calcium-binding capacity of the cardiac form was half the capacity of the skeletal form although the affinities of the two forms of calsequestrin for Ca2+ were similar (Kd = 1 mM). Calcium binding to the cardiac form induced structural changes in the protein as determined by circular dichroism and intrinsic fluorescence spectroscopy. The alpha-helical content of cardiac calsequestrin increased from 3.5% to 10.9% upon binding calcium, while the intrinsic fluorescence of the protein increased 14%. Potassium ions also affected the conformation of cardiac calsequestrin.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Calcium / metabolism
  • Calsequestrin / isolation & purification*
  • Calsequestrin / metabolism
  • Dogs
  • Muscle Proteins / isolation & purification*
  • Muscles / metabolism*
  • Myocardium / metabolism*
  • Organ Specificity
  • Rabbits
  • Species Specificity

Substances

  • Calsequestrin
  • Muscle Proteins
  • Calcium