title: Na+/Ca2+ exchanger in Drosophila: cloning, expression, and transport differences.
abstract: cDNAs for the Na+/Ca2+ exchanger from Drosophila melanogaster (Dmel/Nck) have been cloned by homology screening using the human heart Na+/Ca2+ exchanger cDNA. The overall deduced protein structure for Dmel/Nck is similar to that of mammalian Na+/Ca2+ exchanger genes NCX1 and NCX2, having six hydrophobic regions in the amino terminus separated from six at the carboxy-terminal end by a large intracellular loop. Sequence comparison of the Drosophila exchanger cDNAs with NCX1 and NCX2 Na+/Ca2+ exchangers are approximately 46% identical at the deduced amino acid level. Consensus phosphorylation sites for both protein kinase C and protein kinase A are present on the intracellular loop region of the Dmel/Nck. Alternative splicing for the Dmel/Nck gene is suggested in the same intracellular loop region as demonstrated for NCX1. Functionally, the Drosophila Na+/ Ca2+ exchanger expressed in oocytes differs from expressed mammalian NCX1 with regard to Ca2+ transport in Ca2+/ Ca2+ exchange and the effect of monovalent-dependent Ca2+/ Ca2+ exchange. The Dmel/Nck gene maps to chromosome 3 (93A-B) using in situ hybridization to polytene chromosomes, the same position as the Na(+)-K(+)-ATPase, a related transporter. We conclude that, although extracellular Na+ concentration-dependent Ca2+ transport is subserved by both human and Drosophila Na+/Ca2+ exchangers, there are clear and important differences in the transporters, which should be useful in deducing how the Na+/Ca2+ exchanger protein function depends on its structure.
authors.affiliation: Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, Maryland, USA.
authors.forename: A
authors.initials: A
authors.lastname: Ruknudin
authors.forename: C
authors.initials: C
authors.lastname: Valdivia
authors.forename: P
authors.initials: P
authors.lastname: Kofuji
authors.forename: W J
authors.initials: WJ
authors.lastname: Lederer
authors.forename: D H
authors.initials: DH
authors.lastname: Schulze
mesh_terms: D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D002462:Cell Membrane / Q000502:physiology; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D016384:Consensus Sequence; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D018076:DNA, Complementary / Q000737:chemistry* / Q000378:metabolism; D004330:Drosophila / Q000235:genetics / Q000378:metabolism*; D017344:Genes, Insect; D015698:Genomic Library; D006801:Humans; D017403:In Situ Hybridization; D008322:Mammals; D008969:Molecular Sequence Data; D009865:Oocytes / Q000502:physiology; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D019831:Sodium-Calcium Exchanger; D014981:Xenopus
chemical_list: D002352:Carrier Proteins; D018076:DNA, Complementary; D011994:Recombinant Proteins; D019831:Sodium-Calcium Exchanger; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C