Molecular and Genetic Analysis of the vha16 Gene in Drosophila melanogaster

Vacuolar H+-ATPases (V-ATPases) are multi-subunit enzymes which pump protons across cellular membranes via hydrolysis of ATP. They are related, both in structure and function, to FI-FQ ATP synthases and much about the V-ATPase mode of action has been inferred from FI-FQ studies. V-ATPases have been isolated from a broad phylogenetic range of eukaryotes, from single celled organisms to higher plants and animals. In these higher organisms they can play both endomembrane and plasma membrane roles in a large array of cell types. Several genes encoding subunits of the V-ATPase holoenzyme have been cloned from the model genetic organism Drosophila melanogaster. One of the subunits cloned from D. melanogaster, vhal6, encodes the 16 kDa pore forming protein, through which the hydrogen ions pass. Firstly, this project focuses on this proteolipid gene in Drosophila melanogaster, describing the isolation and characterisation of a lethal P-element insert within the originally described gene, and discussing how the insertion of this element disrupts the normal function of the gene. Also discussed is how this P-element can be used to show the spatial and temporal expression of the gene in vivo. Secondly it describes the isolation of four new homologues of this gene in D. melanogaster. It show's their sequence relationship to the original Drosophila protein, and the protein isolated from other organisms and discusses if they are expressed and whether they would function as V-ATPase pores. This study also describes the attempted rescue of the lethal P-element phenotype with a range of proteolipid sequences cloned from Drosophila and also proteolipids of other organisms. Lastly, this project describes the isolation of two other Drosophila V-ATPase membrane associated subunits, one homologous to PPA1 in yeast and the other homologous to M9.7 in Manduca sexta