A single isoform of the Na+/K(+)-ATPase alpha-subunit in Diptera: evidence from characterization of the first extracellular domain.
The first extracellular domain of the alpha-subunit of the Na+/K+-ATPase (sodium/potassium pump) is functionally important, affecting sensitivity of the enzyme to cardiac glycosides (e.g. ouabain) and being implicated in the transport of K+. This domain is also variable among mammalian isoforms of the alpha-subunit. Using PCR, we have isolated from seven insect species with contrasting physiologies a DNA fragment containing this region, in order to help determine whether tissue-specific expression might be associated with isoforms encoded by a gene family, as it is in mammals. A single sequence (with one ORF) characteristic of Na+/K+-ATPase was obtained from genomic DNA of each species. Only the fragment from Manduca sexta contained an intron, but at a location different to that found in mammals. For all Diptera so far characterized, the species phylogeny is the same as the alpha-subunit gene phylogeny (based on the sequences of the first extracellular domain and flanking transmembrane domains). The results strongly indicate a single, ouabain-sensitive isoform of the alpha-subunit of Na+/K+-ATPase is present in Diptera.
Emery
A M
AM
Department of Entomology, Natural History Museum, London.
Ready
P D
PD
Billingsley
P F
PF
Djamgoz
M B
MB
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D015139:Blotting, Southern; D002874:Chromosome Mapping; D004247:DNA; D004175:Diptera / Q000201:enzymology* / Q000235:genetics; D017344:Genes, Insect; D007527:Isoenzymes / Q000737:chemistry / Q000235:genetics*; D008969:Molecular Sequence Data; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D000254:Sodium-Potassium-Exchanging ATPase / Q000737:chemistry / Q000235:genetics*
D007527:Isoenzymes; D004247:DNA; D000254:Sodium-Potassium-Exchanging ATPase