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Sequence of a Drosophila Ligand‐Gated Ion‐Channel Polypeptide with an Unusual Amino‐Terminal Extracellular Domain
Author(s) -
Harvey Robert J.,
Schmitt Bertram,
HermansBorgmeyer Irm,
Gundelfinger Eckart D.,
Betz Heinrich,
Darlison Mark G.
Publication year - 1994
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.1994.62062480.x
Subject(s) - drosophila melanogaster , biology , complementary dna , protein subunit , exon , amino acid , peptide sequence , microbiology and biotechnology , transmembrane domain , biochemistry , genetics , gene
We report the isolation of a full‐length clone from a Drosophila melanogaster head cDNA library that encodes a 614‐residue polypeptide that exhibits all of the features of a ligand‐gated chloride‐channel/receptor subunit. This polypeptide, which has been named GRD (denoting that the polypeptide is a GABA A and glycine receptor‐like subunit of Drosophila) , displays between 33 and 44% identity to vertebrate GABA A and glycine receptor subunits and 32–37% identity to the GABA A receptor‐like polypeptides from Drosophila and Lymnaea. It is interesting that the large amino‐terminal, presumed extracellular domain of the GRD protein contains an insertion, between the dicysteine loop and the first putative membrane‐spanning domain, of 75 amino acids that is not found in any other ligand‐gated chloride‐channel subunit. Analysis of cDNA and genomic DMA reveals that these residues are encoded by an extension of an exon that is equivalent to exon 6 of vertebrate GABA A and glycine receptor genes. The gene (named Grd) that encodes the Drosophila polypeptide has been mapped, by in situ hybridization, to position 75A on the left arm of chromosome 3.