Cloning and sequencing of thepara-type sodium channel gene from susceptible andkdr-resistant German cockroaches (Blattella germanica) and house fly (Musca domestica)
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- Miyazaki, M., Ohyama, K., Dunlap, D.Y. et al. Molec. Gen. Genet. (1996) 252: 61. doi:10.1007/BF02173205
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Using reverse transcription polymerase chain reactions (RT-PCR), the DNA sequence for the main membrane-spanning region (IS3 through IVS6) of the gene encoding theα-subunit of thepara sodium channel of the German cockroach,Blattella germanica, has been determined. The overall structure of the open reading frame region of thisB. germanica gene is very similar to that of thepara gene ofDrosophila melanogaster, and that of the partially sequencedpara gene ofMusca domestica. On the other hand, it is distinctly different from that of theDSC gene (Drosophila sodium channel). As a result of a side-by-side comparison of thepara gene sequences of the susceptible CSMA strain and thekdr resistant VT strain ofB. germanica, one mutation (TTG to TTC) at the approximate center of the IIS6 membrane-spanning segment was found to result in an amino acid change from L to F. While the functional meaning of this mutation for the operation of thepara sodium channel remains to be studied, this region is very highly conserved among all sodium channels identified so far, and is one of the most hydrophobic areas of the entireα-subunit. For comparison, we have studied the same region of thepara sodium channel of bothkdr and susceptible SBO strain of the housefly,Musca domestica. We found the homologous type of mutation, CTT to TTT, resulting in the same amino acid alteration (L to F) at this site. However, in the case of houseflies bothkdr and susceptible strains contained both L and F versions of the protein. The ratio of TTT to CTT was significantly higher in thekdr strain ofM. domestica than in the three susceptible strains examined.