Calcium binding proteins in the sarcoplasmic/endoplasmic reticulum of muscle and nonmuscle cells

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Abstract
In this paper we review some of the large quantities of information currently available concerning the identification, structure and function of Ca2+-binding proteins of endoplasmic and sarcoplasmic reticulum membranes. The review places particular emphasis on identification and discussion of Ca2+ ‘storage’ proteins in these membranes. We believe that the evidence reviewed here supports the contention that the Ca2+-binding capacity of both calsequestrin and calreticulin favor their contribution as the major Ca2+-binding proteins of muscle and nonmuscle cells, respectively. Other Ca2+-binding proteins discovered in both endoplasmic reticulum and sarcoplasmic reticulum membranes probably contribute to the overall Ca2+ storage capacity of these membrane organelles, and they also play other important functional role such as posttranslational modification of newly synthesized proteins, a cytoskeletal (structural) function, or movement of Ca2+ within the lumen of the sarcoplasmic/endoplasmic reticulum towards the storage sites.