title: Structural basis of the Ca2+ inhibitory mechanism of Drosophila Na+/Ca2+ exchanger CALX and its modification by alternative splicing.
abstract: The Na(+)/Ca(2+) exchanger CALX promotes Ca(2+) efflux in Drosophila sensory neuronal cells to facilitate light-mediated Ca(2+) homeostasis. CALX activity is negatively regulated by specific Ca(2+) interaction within its two intracellular Ca(2+) regulatory domains CBD1 and CBD2, yet how the Ca(2+) binding is converted to molecular motion to operate the exchanger is unknown. Here, we report crystal structures of the entire Ca(2+) regulatory domain CBD12 from two alternative splicing isoforms, CALX 1.1 and 1.2, exhibiting distinct regulatory Ca(2+) dependency. The structures show an open V-shaped conformation with four Ca(2+) ions bound on the CBD domain interface, confirmed by LRET analysis. The structures together with Ca(2+)-binding analysis support that the Ca(2+) inhibition of CALX is achieved by interdomain conformational changes induced by Ca(2+) binding at CBD1. The conformational difference between the two isoforms also indicates that alternative splicing adjusts the interdomain orientation angle to modify the Ca(2+) regulatory property of the exchangers.
authors: Center for Membrane Biology, Department of Biochemistry and Molecular Biology, The University of Texas Houston Medical School, Houston, TX 77030, USA.
authors: Mousheng
authors: M
authors: Wu
authors: Shuilong
authors: S
authors: Tong
authors: Jennifer
authors: J
authors: Gonzalez
authors: Vasanthi
authors: V
authors: Jayaraman
authors: John L
authors: JL
authors: Spudich
authors: Lei
authors: L
authors: Zheng
mesh_terms: D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D017920:Antiporters / Q000737:chemistry*; D001665:Binding Sites; D002118:Calcium / Q000737:chemistry; D002850:Chromatography, Gel; D003001:Cloning, Molecular; D004330:Drosophila / Q000737:chemistry*; D029721:Drosophila Proteins / Q000737:chemistry*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005453:Fluorescence; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D011487:Protein Conformation; D020033:Protein Isoforms / Q000737:chemistry; D017386:Sequence Homology, Amino Acid; D019831:Sodium-Calcium Exchanger / Q000737:chemistry
chemical_list: D017920:Antiporters; C108396:Calx protein, Drosophila; D029721:Drosophila Proteins; D020033:Protein Isoforms; D019831:Sodium-Calcium Exchanger; D002118:Calcium