Chanan Angsuthanasombat, Ph.D.,
|Ph.D. (Biochemistry), University of Cambridge, UK.
Research Interests : Bacterial Protein Toxins
The conserved Asn183 in ?5 was found to be important for the function of the Bacillus thuringiensis Cry4Ba toxin, essentially involved in toxin oligomerisation. Purified Cry4Ba ?4-?5 hairpins were shown to be highly capable of inducing liposome permeability, constituting the region responsible for pore formation within the toxin molecule. We have identified functional elements by demonstrating that two highly conserved aromatic residues, Tyr249 and Phe264, which are oriented on the same side of ?7, play an important role in larvicidal activity of this mosquitoactive toxin. We have also demonstrated that the 21-kDa Cry4Ba-domain III, which can be isolated as a native folded monomer, conceivably participates in toxin-receptor recognition. We have additionally shown that the 43-kDa Cry4Ba fragment comprising domains II and III that was produced in isolation was able to retain its receptor-binding characteristics to the target larval midgut proteins. More recently, we have provided pivotal evidence for the first time that the activated Cry4Ba toxin in association with DMPC lipid membranes could exist in at least two different trimeric conformations, conceivably implying the closed and open states of the pore. For the Bordetella pertussis adenylate cyclase-haemolysin toxin (CyaA), the 126-kDa truncated CyaApore forming fragment (CyaA-PF) was shown for the first time to be highly expressed as a soluble protein in E. coli. In addition, the recombinant CyaA-PF toxin was proved to be palmitoylated at Lys983 via co-expression with CyaC acyltransferase that is necessary for haemolytic activity.