Bacillus thuringiensis (Bt) Vip3A proteins are important insecticidal proteins used for control of lepidopteran insects. However, the mode of action of Vip3A toxin is still unclear. In this study, the amino acid residue S164 in Vip3Aa was identified to be critical for the toxicity in Spodoptera litura. Results from substitution mutations of the S164 indicate that the insecticidal activity of Vip3Aa correlated with the formation of a >240 kDa complex of the toxin upon proteolytic activation. The >240 kDa complex was found to be composed of the 19 kDa and the 65 kDa fragments of Vip3Aa. Substitution of the S164 in Vip3Aa protein with Ala or Pro resulted in loss of the >240 kDa complex and loss of toxicity in Spodoptera litura. In contrast, substitution of S164 with Thr did not affect the >240 kDa complex formation, and the toxicity of the mutant was only reduced by 35%. Therefore, the results from this study indicated that formation of the >240 kDa complex correlates with the toxicity of Vip3Aa in insects and the residue S164 is important for the formation of the complex. Key Contribution:Our results correlated the formation of a >240 kDa protein complex with the insecticidal activity of Vip3Aa toxin. The residue S164 in Vip3Aa protein was identified to be important for the formation of the >240 kDa protein complex.

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Background and Aim Upper gastrointestinal bleeding is a rare and potentially life‐threatening condition in children. Herein, clinical features and risk factors in children with upper gastrointestinal bleeding were analyzed, and a clinical scoring system was constructed to assess severity. Methods This retrospective cohort study involved 224 children hospitalized with upper gastrointestinal bleeding between January 2012 and April 2018. Demographic data, clinical information, and laboratory test results on admission were statistically examined. Results Out of 224 upper gastrointestinal bleeding cases, 76 were diagnosed as severe and 148 as mild cases according to the rate of blood loss and severity. Severe group was significantly different from mild group in 23 items including age, number of patients aged more than 7 years, and so forth (P < 0.01 or P < 0.05). Positive detection rate of bleeding etiology was gradually decreased (P < 0.01) in relation to delay in timing of endoscopy. Analysis of logistic regression evinced five independent risk factors for severe cases to be associated with poor consciousness, hemoglobin < 80 g/L, hemoglobin drop of > 20 g/L, hematochezia, and anemic appearance (P < 0.01 or P < 0.05). Using these five parameters, a number of scoring models were tested. The most predictive resulted in a scoring system constructed with a total of 16 and a cutoff for intervention of 8. Conclusions Amalgamation of risk factors with the scoring system plays an important role in assessing upper gastrointestinal bleeding severity in children.

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