Apocalmodulin and Ca2+ Calmodulin Bind to the Same Region on the Skeletal Muscle Ca2+ Release Channel
- 1 June 1999
- journal article
- research article
- Published by American Chemical Society (ACS) in Biochemistry
- Vol. 38 (26) , 8532-8537
- https://doi.org/10.1021/bi9907431
Abstract
The skeletal muscle Ca2+ release channel (RYR1) is regulated by calmodulin in both its Ca2+-free (apocalmodulin) and Ca2+-bound (Ca2+ calmodulin) states. Apocalmodulin is an activator of the channel, and Ca2+ calmodulin is an inhibitor of the channel. Both apocalmodulin and Ca2+ calmodulin binding sites on RYR1 are destroyed by a mild tryptic digestion of the sarcoplasmic reticulum membranes, but calmodulin (either form), bound to RYR1 prior to tryptic digestion, protects both the apocalmodulin and Ca2+ calmodulin sites from tryptic destruction. The protected sites are after arginines 3630 and 3637 on RYR1. These studies suggest that both Ca2+ calmodulin and apocalmodulin bind to the same or overlapping regions on RYR1 and block access of trypsin to sites at amino acids 3630 and 3637. This sequence is part of a predicted Ca2+ CaM binding site of amino acids 3614−3642 [Takeshima, H., et al. (1989) Nature339, 439−445].Keywords
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