Lobe-dependent regulation of ryanodine receptor type 1 by calmodulin.
Calmodulin activates the skeletal muscle Ca(2+) release channel RYR1 at nm Ca(2+) concentrations and inhibits the channel at microm Ca(2+) concentrations. Using a deletion mutant of calmodulin, we demonstrate that amino acids 2-8 are required for high affinity binding of calmodulin to RYR1 at both nm and microm Ca(2+) concentrations and are required for maximum inhibition of the channel at microm Ca(2+) concentrations. In contrast, the addition of three amino acids to the N terminus of calmodulin increased the affinity for RYR1 at both nm and microm Ca(2+) concentrations, but destroyed its functional effects on RYR1 at nm Ca(2+). Using both full-length RYR1 and synthetic peptides, we demonstrate that the calmodulin-binding site on RYR1 is likely to be noncontiguous, with the C-terminal lobe of both apocalmodulin and Ca(2+)-calmodulin binding to amino acids between positions 3614 and 3643 and the N-terminal lobe binding at sites that are not proximal in the primary sequence. Ca(2+) binding to the C-terminal lobe of calmodulin converted it from an activator to an inhibitor, but an interaction with the N-terminal lobe was required for a maximum effect on RYR1. This interaction apparently depends on the native sequence or structure of the first few amino acids at the N terminus of calmodulin.
Department of Molecular Physiology and Biophysics, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX 77030, USA.
Liang-Wen
LW
Xiong
Rhonda A
RA
Newman
George G
GG
Rodney
Oluwatoyin
O
Thomas
Jia-Zheng
JZ
Zhang
Anthony
A
Persechini
Madeline A
MA
Shea
Susan L
SL
Hamilton
D000818:Animals; D002147:Calmodulin / Q000737:chemistry / Q000502:physiology*; D004591:Electrophoresis, Polyacrylamide Gel; D018482:Muscle, Skeletal / Q000378:metabolism; D017433:Protein Structure, Secondary; D011817:Rabbits; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism / Q000502:physiology*; D013050:Spectrometry, Fluorescence
D002147:Calmodulin; D019837:Ryanodine Receptor Calcium Release Channel
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