The BinAB toxin, produced in crystal form by a bacterium, specifically kills the larvae of Culex and Anopheles mosquitoes, but it is inactive on Aedes mosquitoes, the vectors for dengue, chikungunya, and zika viruses. Knowledge of the molecular structure of BinAB is necessary if scientists are to broaden its spectrum of action. Having long been inaccessible, this structure has been published online on September 28, 2016 in Nature by an international consortium involving scientists from the multiple institutions. The Nature article is titled “De novo Phasing with X-Ray Laser Reveals Mosquito Larvicide BinAB Structure.” Mosquitoes are vectors for numerous devastating diseases, including malaria that is spread by Anopheles mosquitoes, and filariasis transmitted by Culex mosquitoes. The BinAB toxin, produced in the form of nanocrystals by the bacterium Bacillus sphaericus, specifically targets the larvae of these two groups of mosquitoes. A complex, five-step intoxication process (see description below) explains the environmental safety of BinAB, which is harmless to other insects, crustaceans, and humans. BinAB is therefore used in many countries to regulate mosquito populations. Unfortunately, the strength of BinAB is also its weakness: the toxin is ineffective on the larvae of Aedes mosquitoes, which spread the viruses for dengue, zika, and chikungunya. A remodeling of BinAB might allow a broadening of its spectrum, but to achieve this it is necessary to understand its structure. X-ray crystallography is an excellent method to reveal the structure of a protein, but it is generally only applicable to large crystals measuring approximately a tenth of a millimeter.
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