De novo phasing with X-ray laser reveals mosquito larvicide BinAB structure

• Published in: Nature (London) 2016-11, Vol.539 (7627), p.43-47
• Main Authors: Colletier, Jacques-Philippe, Sawaya, Michael R., Gingery, Mari, Rodriguez, Jose A., Cascio, Duilio, Brewster, Aaron S., Michels-Clark, Tara, Hice, Robert H., Coquelle, Nicolas, Boutet, Sébastien, Williams, Garth J., Messerschmidt, Marc, DePonte, Daniel P., Sierra, Raymond G., Laksmono, Hartawan, Koglin, Jason E., Hunter, Mark S., Park, Hyun-Woo, Uervirojnangkoorn, Monarin, Bideshi, Dennis K., Brunger, Axel T., Federici, Brian A., Sauter, Nicholas K., Eisenberg, David S.
• Format: Article
• Language: English
• Subjects: 38/22; 38/77; 60 APPLIED LIFE SCIENCES; 631/1647/2258/1266/1265; 631/535/1266/1265; 631/61/168; 631/61/2297; 82/80; Animals; Aquatic insects; Bacillus - chemistry; Bacterial Toxins - chemistry; Binding Sites; Biochemistry, Molecular Biology; Crystal structure; Crystallization; Crystallography; Crystallography, X-Ray; Crystals; Culicidae - metabolism; environmental biotechnology; Health aspects; Humanities and Social Sciences; Hydrogen-Ion Concentration; Insecticides - chemistry; INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; Larva - chemistry; Larva - metabolism; Larvicides; Lasers; Life Sciences; Models, Molecular; Mosquitoes; multidisciplinary; nanocrystallography; Observations; Pesticide residues; Pesticides; protein delivery; Protein Multimerization; Proteolysis; Science; Structural Biology; Toxicity; Toxins; Tyrosine - chemistry; X-ray lasers
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/nature19825

BinAB is a naturally occurring paracrystalline larvicide distributed worldwide to combat the devastating diseases borne by mosquitoes. These crystals are composed of homologous molecules, BinA and BinB, which play distinct roles in the multi-step intoxication process, transforming from harmless, robust crystals, to soluble protoxin heterodimers, to internalized mature toxin, and finally to toxic oligomeric pores. The small size of the crystals—50 unit cells per edge, on average—has impeded structural characterization by conventional means. Here we report the structure of Lysinibacillus sphaericus BinAB solved de novo by serial-femtosecond crystallography at an X-ray free-electron laser. The structure reveals tyrosine- and carboxylate-mediated contacts acting as pH switches to release soluble protoxin in the alkaline larval midgut. An enormous heterodimeric interface appears to be responsible for anchoring BinA to receptor-bound BinB for co-internalization. Remarkably, this interface is largely composed of propeptides, suggesting that proteolytic maturation would trigger dissociation of the heterodimer and progression to pore formation. The structure of the bacterial toxin BinAB, which is used to combat mosquito-borne diseases, reveals pH-sensitive switches and carbohydrate-binding modules that may contribute to the larvicidal function of the toxin. Structure of the mosquito larvicide BinAB Mosquitoes continue to be the insects most injurious to human health, because they act as a vector for several infectious diseases including malaria, dengue fever, West Nile encephalitis, and Zika virus. The Lysinibacillus sphaericus binary toxin BinAB is distributed worldwide to combat mosquito-borne diseases, because these proteins are toxic to their targets, but harmless to humans and other animals. These authors used serial-femtosecond crystallography at an X-ray free-electron laser source to solve the structure of BinAB crystals. The structure reveals four pH-sensitive switches that facilitate crystal dissolution in the larval midgut as well as three carbohydrate-binding modules in BinA that may assist in directing heterodimers to the cell surface.