PT-TG is a conserved region found in many bacterial toxin proteins. It could function as a linker that links N-terminal secretion-related domain and C-terminal toxin domain. It contains a TG motif [1].

1: A novel immunity system for bacterial nucleic acid degrading toxins and its recruitment in various eukaryotic and DNA viral systems. Zhang D, Iyer LM, Aravind L; Nucleic Acids Res. 2011;39:4532-4552. PMID:21306995