Expression and characterization of a novel class of glutathione S-transferase from Anopheles dirus

A new Anopheles dirus glutathione S-transferase (GST) has been obtained and named adGST4-1. Both genomic DNA and cDNA for heterologous expression were acquired. The genomic sequence was 3188bp and consisted of the GST gene as well as flanking sequence. The flanking sequence was analyzed for possible regulatory elements that would control gene expression. In Drosophila several of these elements have been shown to be involved in development and cell differentiation. The deduced amino acid sequence has low identity compared with the four alternatively spliced enzymes, adGST1-1 to 1-4, from another An. dirus GST gene adgst1AS1. The percent identities are 30--40% and 11--12% comparing adGST4-1 to insect GSTs from Delta and Sigma classes, respectively. Enzyme characterization of adGST4-1 shows it to be distinct from the other An. dirus GSTs because of low enzyme activity for customary GST substrates including 1-chloro-2, 4-dinitrobenzene (CDNB). However, this enzyme has a greater affinity of interaction with pyrethroids compared to the other An. dirus GSTs.