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Differential proteolytic activation of the Bacillus thuringiensis Cry41Aa parasporin modulates its anticancer effect
journal contribution
posted on 2023-06-09, 20:01 authored by Wided Souissi, Arnold Kaloki, Stuart Etherington, Barbara Domanska, Michelle WestMichelle West, Neil CrickmoreNeil CrickmoreBacillus thuringiensis (Bt) is a gram positive spore forming bacterium which produces intracellular protein crystals toxic to a wide variety of insect larvae and is the most commonly used biological pesticide worldwide. More recently, Bt crystal proteins known as parasporins have been discovered, that have no known insecticidal activity but target some human cancer cells exhibiting strong cytocidal activities with different toxicity spectra and varied activity levels. Parasporin-3, also called Cry41Aa, has only been shown to exhibit cytocidal activity towards HL-60 (Human promyelocytic leukemia cells) and HepG2 (Human liver cancer cells) cell lines after being proteolytically cleaved. In order to understand this activation mechanism various mutations were made in the N-terminal region of the protein and the toxicity against both HepG2 and HL-60 cell lines was evaluated. Our results indicate that only N-terminal cleavage is required for activation and that N-terminally deleted mutants show some toxicity without the need for proteolytic activation. Furthermore we have shown that the level of toxicity towards the two cell lines depends on the protease used to activate the toxin. Proteinase K-activated toxin was significantly more toxic towards HepG2 and HL-60 than trypsin-activated toxin. N-terminal sequencing of activated toxins showed that this difference in toxicity is associated with a difference of just two amino acids (serine and alanine at positions 59 and 60 respectively) which we hypothesize occlude a binding motif.
History
Publication status
- Published
File Version
- Accepted version
Journal
Biochemical JournalISSN
0264-6021Publisher
Portland PressExternal DOI
Issue
24Volume
476Page range
3805-3816Department affiliated with
- Biochemistry Publications
Full text available
- Yes
Peer reviewed?
- Yes
Legacy Posted Date
2020-01-02First Open Access (FOA) Date
2020-12-24First Compliant Deposit (FCD) Date
2019-12-20Usage metrics
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