title: A Ca2+-binding domain in RyR1 that interacts with the calmodulin binding site and modulates channel activity.
abstract: A fragment of RyR1 (amino acids 4064-4210) is predicted to fold to at least one lobe of calmodulin and to bind Ca(2+). This fragment of RyR1 (R4064-4210) was subcloned, expressed, refolded, and purified. Consistent with the predicted folding pattern, R4064-4210 was found to bind two molecules of Ca(2+) and undergo a structural change upon binding Ca(2+) that exposes hydrophobic amino acids. R4064-4210 also binds to RyR1, the L-type Ca(2+) channel (Cav(1.1)), and several synthetic calmodulin binding peptides. Both R4064-4210 and a peptide representing the calmodulin-binding region of RyR1 (R3614-3643) alter the Ca(2+) dependence of ((3)H)ryanodine binding to RyR1, suggesting that they may both be interfering with an intramolecular interaction between amino acids 4064-4210 and amino acids 3614-3643 in the native RyR1 to alter or regulate the response of the channel to changes in Ca(2+) concentration. The finding that a domain within RyR1 binds Ca(2+) and interacts with calmodulin-binding motifs may provide insights into the mechanism for calcium- and calmodulin-dependent regulation of this channel and perhaps for its regulation by the L-type Ca(2+) channel.
authors.affiliation: Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, Texas, USA.
authors.forename: Liangwen
authors.initials: L
authors.lastname: Xiong
authors.forename: Jia-Zheng
authors.initials: JZ
authors.lastname: Zhang
authors.forename: Rong
authors.initials: R
authors.lastname: He
authors.forename: Susan L
authors.initials: SL
authors.lastname: Hamilton
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000737:chemistry; D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000737:chemistry / Q000378:metabolism*; D020746:Calcium Channels, L-Type / Q000737:chemistry; D002147:Calmodulin / Q000737:chemistry*; D002942:Circular Dichroism; D004247:DNA / Q000737:chemistry; D004926:Escherichia coli / Q000378:metabolism; D021621:Imaging, Three-Dimensional; D008968:Molecular Conformation; D008969:Molecular Sequence Data; D010247:Paramecium; D010455:Peptides / Q000737:chemistry; D011485:Protein Binding; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011817:Rabbits; D012433:Ryanodine / Q000737:chemistry; D017386:Sequence Homology, Amino Acid; D013050:Spectrometry, Fluorescence
chemical_list: D000596:Amino Acids; D020746:Calcium Channels, L-Type; D002147:Calmodulin; D010455:Peptides; D012433:Ryanodine; D004247:DNA; D002118:Calcium