Histamine, a neurotransmitter and neuroregulatory compound in diverse species, serves as the neurotransmitter of photoreceptors in insects and other arthropods by directly activating a chloride channel. By systematic expression screening of novel putative ligand-gated anion channels, we identified two cDNAs (DM-HisCl-alpha 1 and-alpha 2) coding for putative histamine-gated chloride channels by functional expression in Xenopus laevis oocytes. DM-HisCl-alpha 1 mRNA localizes in the lamina region of the Drosophila eye, supporting the idea that DM-HisCl-alpha 1 may be a neurotransmitter receptor for histamine in the visual system.

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We have characterized two previously cloned genes, F1 and F2 (1) that code for elongation factor EF - 1 alpha of Drosophila melanogaster. Genomic Southern blot hybridization revealed that they are the only gene copies present. We isolated cDNA clones of both transcripts from embryonal and pupal stage of development that cover the entire transcription unit. The 5' ends of both genes have been determined by primer extension and for F1 also by RNA sequencing. These start sites have been shown to be used consistently during development. Comparison of cDNA and genomic sequences revealed that EF - 1 alpha,F1 consists of two and EF - 1 alpha,F2 of five exons. The two described elongation factor genes exhibit several regions of strong sequence conservation when compared to five recently cloned eucaryotic elongation factors.

Acetylcholine is a major excitatory neurotransmitter in the central nervous system of insects. Using DNA probes of the Torpedo nicotinic acetylcholine receptor (AChR) we have isolated two overlapping cDNA clones encoding a putative neuronal AChR protein from the fruitfly, Drosophila melanogaster. The predicted mature protein consists of 497 amino acids, has a calculated mol. wt of 57 340 and shows extensive homology to known AChR subunits from different species along its entire amino acid sequence. Northern analysis revealed a hybridizing mRNA of 3.2 kb in late embryo and in pupae. Expression of the corresponding AChR gene thus characterizes periods of neuronal differentiation in Drosophila.

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