%0 Journal Article %A Al-yahyaee, Said A. S. %A Ellar, David J. %T Maximal toxicity of cloned CytA δ-endotoxin from Bacillus thuringiensis subsp. israelensis requires proteolytic processing from both the N- and C-termini %D 1995 %J Microbiology, %V 141 %N 12 %P 3141-3148 %@ 1465-2080 %R https://doi.org/10.1099/13500872-141-12-3141 %K Bacillus thuringiensis %K haemolytic assay %K CytA %K δ-endotoxins %I Microbiology Society, %X Unlike the CytA toxin from native Bacillus thuringiensis subsp. israelensis (Bti) crystals, the inclusions of cloned CytA produced by Bti IPS 78/11 in the presence of the 20 kDa ‘helper’ protein require a reducing agent in addition to a highly alkaline pH for complete solubilization. Activation of the solubilized CytA with a range of proteases produced 25-22 kDa products. SDS-PAGE analysis and N-terminal amino acid sequencing revealed that CytA was processed very similarly at both termini by proteinase K or by Anopheles or Culex gut extracts. Trypsin, by contrast, processed CytA predominantly at the N-terminus. In vitro cytolytic assays against Aedes aegypti cells, and haemolytic assays against rat erythrocytes, showed that CytA processed at both termini by proteinase K was the most active form. Thus CytA, like other Bt δ-endotoxins, is processed to a well-defined protease-resistant product and this processing enhances the toxicity in vitro and possibly in vivo. %U https://www.microbiologyresearch.org/content/journal/micro/10.1099/13500872-141-12-3141