Chitsirin LailakTararat KhaokhiewChamras PromptmasBoonhiang PromdonkoyKusol PootanakitChanan AngsuthanasombatMahidol UniversityThailand National Center for Genetic Engineering and Biotechnology2018-10-192018-10-192013-05-31Biochemical and Biophysical Research Communications. Vol.435, No.2 (2013), 216-221109021040006291X2-s2.0-84878427784https://repository.li.mahidol.ac.th/handle/123456789/31307We previously demonstrated that co-expression in Escherichia coli of Bacillus thuringiensis (Bt) subsp. israelensis Cry4Ba and Bt subsp. darmstadiensis Cyt2Aa2 shows high synergistic toxicity against target mosquito larvae. Here, further insights into synergistic interactions between these two toxins were revealed through bioactivity restoration of particular inactive Cry4Ba-mutant toxins altered within the receptor-binding domain. Specific mutations at β2-β3 (Y332A) or β4-β5 (F364A) loops, but neither at three other β-hairpin loops (β6-β7, β8-β9 and β10-β11) of Cry4Ba, adversely affect toxicity restoration by Cyt2Aa2. Binding analysis using quartz crystal microbalance verified a decrease in binding of these two bioinactive-mutant toxins (Y332A and F364A) to the immobilized Cyt2Aa2. This suggests that Cry4Ba utilizes these two critical aromatic loop-residues, Tyr332and Phe364, for synergistic toxicity with its alternative receptor-Cyt2Aa2. © 2013 .Mahidol UniversityBiochemistry, Genetics and Molecular BiologyArticleSCOPUS10.1016/j.bbrc.2013.04.078