title: Interaction of Lysinibacillus sphaericus Cry48Aa/Cry49Aa toxin with midgut brush-border membrane fractions from Culex quinquefasciatus larvae.
abstract: The Cry48Aa/Cry49Aa mosquitocidal toxin from Lysinibacillus sphaericus was uniquely composed of a three-domain (Cry) toxin and binary (Bin) toxin-like protein, with high toxicity against Culex spp. However, its mode of action against the target mosquitoes is still unknown. In this study, Cry48Aa, Cry49Aa and its N- and C-terminal truncated proteins were expressed and purified, and the binding affinities of the purified proteins with midgut brush-border membrane fractions (BBMFs) from Culex quin-quefasciatus larvae were performed. The results showed that both Cry48Aa and Cry49Aa have specific and high binding affinity to BBMFs, with dissociation constants of 9.5 ± 1.8 and 25.4 ± 3.8 nM, respectively. Competition assays demonstrated that Cry49Aa C-terminal derivatives were able to bind to the BBMFs, whereas Far-Western dot blot analysis revealed that its N-terminal constructs interacted with Cry48Aa. Nevertheless, larvicidal activity was almost lost when Cry49Aa truncated proteins, either individually or in pairs, combined with Cry48Aa. It is concluded that Cry49Aa is responsible for receptor binding and interaction with Cry48Aa and plays an important role in the mechanism of action of these two-component toxins.
authors.affiliation: College of Life and Environmental Sciences, Gannan Normal University, Ganzhou, China.
authors.forename: Q-Y
authors.initials: QY
authors.lastname: Guo
authors.affiliation: Key Laboratory of Agricultural and Environmental Microbiology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China.
authors.forename: X-M
authors.initials: XM
authors.lastname: Hu
authors.affiliation: Key Laboratory of Agricultural and Environmental Microbiology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China.
authors.forename: Q-X
authors.initials: QX
authors.lastname: Cai
authors.affiliation: Key Laboratory of Agricultural and Environmental Microbiology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China.
authors.forename: J-P
authors.initials: JP
authors.lastname: Yan
authors.affiliation: Key Laboratory of Agricultural and Environmental Microbiology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China.
authors.forename: Z-M
authors.initials: ZM
authors.lastname: Yuan
mesh_terms: D000818:Animals; D001407:Bacillus / Q000737:chemistry; D001427:Bacterial Toxins / Q000737:chemistry / Q000494:pharmacology*; D002462:Cell Membrane / Q000187:drug effects; D003465:Culex / Q000737:chemistry / Q000187:drug effects*; D004064:Digestive System / Q000737:chemistry; D007814:Larva / Q000737:chemistry / Q000187:drug effects*; D008871:Microvilli / Q000187:drug effects
chemical_list: D001427:Bacterial Toxins
keywords: Cry48Aa/Cry49Aa toxin; Culex quinquefasciatus; Lysinibacillus sphaericus; interaction; larvicidal activity