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1.C.106 The Bacillus thuringiensis Vegetative Insecticidal Protein-2 (Vip2) Family

Vegetative insecticidal proteins (Vip), the second generation of insecticides, are produced during the vegetative growth stage of Bacillus thuringiensis. Vips fall into three families, Vip1 (TC#1.C.42), Vip2 (this family) and Vip3 (1.C.105). They form transmembrane pores that kill the cells of the target insect (Sauka et al. 2012). Vip2 family members have been isolated from a variety of B. thuringiensis sources (Sattar and Maiti 2011; Yu et al. 2011). Vip2 proteins may have an internal duplication. Isoforms may form binary toxins that require the formation of a complex between Vip1 and Vip2 (Sattar and Maiti 2011).

ExoS and ExoT (1.C.106.4) are bi-functional type-III cytotoxins of Pseudomonas aeruginosa that share 75% identity and contain N-terminal RhoGAP domains and C-terminal ADP-ribosylation domains. The Rho GAP activities of ExoS and ExoT appear to be biochemically identical, targeting Rho, Rac, and Cdc42 (Barbieri and Sun 2004). Expression of the RhoGAP domain in mammalian cells results in the disruption of the actin cytoskeleton and interference of phagocytosis. Expression of the ADP-ribosyltransferase domain of ExoS elicits a cytotoxic phenotype in cultured cells, while expression of ExoT appears to interfere with host cell phagocytic activity. ExoS and ExoT ADP-ribosylate different substrates. While ExoS has poly-substrate specificity and can ADP-ribosylate numerous host proteins, ExoT ADP-ribosylates a more restricted subset of host proteins (Barbieri and Sun 2004).

References associated with 1.C.106 family:

Barbieri, J.T. and J. Sun. (2004). Pseudomonas aeruginosa ExoS and ExoT. Rev Physiol Biochem Pharmacol 152: 79-92. 15375697
Cisz, M., P.C. Lee, and A. Rietsch. (2008). ExoS controls the cell contact-mediated switch to effector secretion in Pseudomonas aeruginosa. J. Bacteriol. 190: 2726-2738. 18039770
Russell, A.B., S.B. Peterson, and J.D. Mougous. (2014). Type VI secretion system effectors: poisons with a purpose. Nat. Rev. Microbiol. 12: 137-148. 24384601
Sattar, S. and M.K. Maiti. (2011). Molecular characterization of a novel vegetative insecticidal protein from Bacillus thuringiensis effective against sap-sucking insect pest. J Microbiol Biotechnol 21: 937-946. 21952370
Sauka, D.H., S.E. Rodriguez, and G.B. Benintende. (2012). New Variants of Lepidoptericidal Toxin Genes Encoding Bacillus thuringiensis Vip3Aa Proteins. J. Mol. Microbiol. Biotechnol. 22: 373-380. 23307196
Wood, S.J., J.W. Goldufsky, D. Bello, S. Masood, and S.H. Shafikhani. (2015). Pseudomonas aeruginosa ExoT Induces Mitochondrial Apoptosis in Target Host Cells in a Manner That Depends on Its GTPase-activating Protein (GAP) Domain Activity. J. Biol. Chem. 290: 29063-29073. 26451042
Yu, X., A. Zheng, J. Zhu, S. Wang, L. Wang, Q. Deng, S. Li, H. Liu, and P. Li. (2011). Characterization of vegetative insecticidal protein vip genes of Bacillus thuringiensis from Sichuan Basin in China. Curr. Microbiol. 62: 752-757. 20963416