Bifunctional sesterterpene synthase that possesses both prenyl transferase and terpene cyclase activity, converting isopentenyl diphosphate and dimethylallyl diphosphate into geranylfarnesyl diphosphate (GFPP) and further converting GFPP into sesterbrasiliatriene. (2E,6E)-farnesyl diphosphate + isopentenyl diphosphate = (2E,6E,10E)-geranylgeranyl diphosphate + diphosphate (2E,6E,10E)-geranylgeranyl diphosphate + isopentenyl diphosphate = (2E,6E,10E,14E)-geranylfarnesyl diphosphate + diphosphate Secondary metabolite biosynthesis; terpenoid biosynthesis. Hexamer. The conserved DDXXD motifs as well as the NSE/DTE motif are important for the catalytic activity, presumably through binding to Mg(2+). In the N-terminal section; belongs to the terpene synthase family. In the C-terminal section; belongs to the FPP/GGPP synthase family.