Characterization of cardiac calsequestrin

• Published in: Biochemistry (Easton) Vol. 26; no. 20; pp. 6539 - 6544
• Main Authors: Slupsky, Joseph R, Ohnishi, Mamoru, Carpenter, Michael R, Reithmeier, Reinhart A. F
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 06.10.1987
• Subjects: Amino Acid Sequence; Analytical, structural and metabolic biochemistry; Animals; Binding and carrier proteins; Biological and medical sciences; Calcium - metabolism; calsequestrin; Calsequestrin - isolation & purification; Calsequestrin - metabolism; cardiac muscle; Dogs; Fundamental and applied biological sciences. Psychology; Muscle Proteins - isolation & purification; Muscles - metabolism; Myocardium - metabolism; Organ Specificity; Proteins; Rabbits; Species Specificity; Heart; Fissipedia; Carnivora; Purification; Rabbit; Lagomorpha; Calcium Ions; Secondary structure; Binding protein; Vertebrata; Mammalia; N terminal-Sequence; Muscle; Dog
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi00394a038

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.