Biochemical analysis of a blood meal-induced Aedes aegypti glutamine synthetase gene

Glutamine synthetase (GS) in the mosquito, Aedes aegypti, is induced in the midgut following a blood meal. Mosquito GS message is detected as soon as 1 h post-blood feeding and remains stable for 18 h. Using a PCR product enc oding mosquito GS, a lambda gt10 adult female mosquito cDNA library was scr eened. A cDNA clone, pCl5A2, encoding the full translation product of mosqu ito GS was isolated and sequence analyses performed. Mosquito GS cDNA is 2. 5 kb in length and its putative translation product shares all the conserve d regions characteristic of the GS gene family, including the presumed ATP biding site. Glutamine synthetase activity in the mosquito midgut is highes t at 18 h post-blood feeding. Activity can be detected over a broad pH rang e, from 6.0 to 7.5. Unlike other cellular GS enzymes, mosquito GS is not ac tive in the presence of ATP. Very low dosages (0.05 mM) of L-methionine S-s ulfoximine are sufficient to partially inhibit mosquito GS activity. Inhibi tion of GS disrupts the normal formation of the midgut peritrophic matrix, suggesting that GS enzyme might be involved in the initial pathway of chiti n synthesis. The unique expression pattern and inducible nature of the mosq uito GS gene make it an interesting candidate for studying promoter functio n. Additionally, the blood meal activation of the GS gene makes this a pote ntially valuable tool in mosquito transformation studies. (C) 1998 Elsevier Science Ltd. All rights reserved.