Trichothecenes are the secondary metabolites produced by Trichoderma spp. Some of these molecules have been reported for their ability to stimulate plant growth by suppressing plant diseases and hence enabling Trichoderma spp. to be efficiently used as biocontrol agents in modern agriculture. Many of the proteins involved in the trichothecenes biosynthetic pathway in Trichoderma spp. are encoded by the genes present in the tri cluster. Tri4 protein catalyzes three consecutive oxygenation reaction steps during biosynthesis of isotrichodiol in the trichothecenes biosynthetic pathway, while tri11 protein catalyzes the C4 hydroxylation of 12, 13-epoxytrichothec-9-ene to produce trichodermol. In the present study, we have homology modelled the three-dimensional structures of tri4 and tri11 proteins. Furthermore, molecular dynamics simulations were carried out to elucidate the mechanism of their action. Both tri4 and tri11 encode for cytochrome P450 monooxygenase like proteins. These data also revealed effector-induced allosteric changes on substrate binding at an alternative binding site and showed potential homotropic negative cooperativity. These analyses also showed that their catalytic mechanism relies on protein-ligand and protein-heme interactions controlled by hydrophobic and hydrogen-bonding interactions which orient the complex in optimal conformation within the active sites.
Keywords: 12, 13-epoxytrichothec-9-ene; Cytochrome P450 monooxygenase; Homotropic cooperativity; Trichoderma brevicompactum; Trichodiene.