Ganesh N. PandianToshiki IshikawaThangavel VaijayanthiDelwar M. HossainShuhei YamamotoTadayuki NishiumiChanan AngsuthanasombatKohsuke HaginoyaToshiaki MitsuiHidetaka HoriNiigata UniversityMahidol University2018-09-242018-09-242010-10-01Journal of Membrane Biology. Vol.237, No.2-3 (2010), 125-136002226312-s2.0-78649970541https://repository.li.mahidol.ac.th/handle/20.500.14594/28625P252, a 252-kDa Bombyx mori protein located on the larval midgut membrane, has been shown to bind strongly with Bacillus thuringiensis Cry1A toxins (Hossain et al. Appl Environ Microbiol 70:4604-4612, 2004). P252 was also shown to bind chlorophyllide (Chlide) to form red fluorescence-emitting complex Bm252RFP with significant antimicrobial activity (Pandian et al. Appl Environ Microbiol 74:1324-1331, 2008). In this article, we show that Cry1A toxin bound with Bm252RFP and Bm252RFP-Cry1A macrocomplex, with both antimicrobial and insecticidal activities, was formed. The insecticidal activity of Bm252RFP-Cry1Ab was reduced from an LD50 of 1.62 to 5.05 μg, but Bm252RFP-Cry1Aa and Bm252RFP-Cry1Ac did not show such reduction. On the other hand, the antimicrobial activity of Bm252RFP-Cry1Ab was shown to retain almost the same activity as Bm252RFP, while the other two complexes lost around 30% activity. The intensity of photo absorbance and fluorescence emission of Bm252RFP-Cry1Ab were significantly reduced compared to those of the other two complexes. Circular dichroism showed that the contents of Cry1Ab α-helix was significantly decreased in Bm252RFP-Cry1Ab but not in the other two toxins. These data suggested that the reduction of contents of α-helix in Cry1Ab affected the insecticidal activity of the macrocomplex but did not alter the antimicrobial moiety in the macrocomplex of Bm252RFP-Cry1Ab. © 2010 Springer Science+Business Media, LLC.Mahidol UniversityBiochemistry, Genetics and Molecular BiologyArticleSCOPUS10.1007/s00232-010-9314-x