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An alpha-helical C-terminal tail segment of the skeletal L-type Ca2+ channel beta1a subunit activates ryanodine receptor type 1 via a hydrophobic surface




Karunasekara, Yamuna
Rebbeck, Robyn
Weaver, Llara
Board, Philip
Dulhunty, Angela
Casarotto, Marco

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Federation of American Societies for Experimental Biology


Excitation-contraction (EC) coupling in skeletal muscle depends on protein interactions between the transverse tubule dihydropyridine receptor (DHPR) voltage sensor and intracellular ryanodine receptor (RyR1) calcium release channel. We present novel data showing that the C-terminal 35 residues of the β1a subunit adopt a nascent α-helix in which 3 hydrophobic residues align to form a hydrophobic surface that binds to RyR1 isolated from rabbit skeletal muscle. Mutation of the hydrophobic residues (L496, L500, W503) in peptide β1aV490-M524, corresponding to the C-terminal 35 residues of β1a, reduced peptide binding to RyR1 to 15.2 ± 7.1% and prevented the 2.9 ± 0.2-fold activation of RyR1 by 10 nM wild-type peptide. An upstream hydrophobic heptad repeat implicated in β1a binding to RyR1 does not contribute to RyR1 activation. Wild-type β1aA474-A508 peptide (10 nM), containing heptad repeat and hydrophobic surface residues, increased RyR1 activity by 2.3 ± 0.2- and 2.2 ± 0.3-fold after mutation of the heptad repeat residues. We conclude that specific hydrophobic surface residues in the 35 residue β1a C-terminus bind to RyR1 and increase channel activity in lipid bilayers and thus may support skeletal EC coupling.



Keywords: 1,4 dihydropyridine receptor; amino acid; beta1a peptide; calcium channel L type; carboxy terminal telopeptide; ryanodine receptor 1; unclassified drug; alpha helix; animal tissue; article; carboxy terminal sequence; enzyme activity; excitation contractio Excitation-contraction coupling; Protein-protein interaction



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