Toxic component of a contact-dependent interbacterial competition system (also called effector-immunity systems). Acts by ADP-ribosylating a number of target proteins in target cells; E.coli target proteins include FtsZ, EFTu, RNase E, Fis, RL9, SucB, and LolD. FtsZ is thought to be the physiologically relevant target as it is ADP-ribosylated on a critical residue. ADP-ribosylation of FtsZ prevents formation of the FtsZ mid-cell ring and inhibits cell division. Overexpression of the whole Tre1 protein or the ART domain in E.coli is toxic; cells elongate dramatically and some undergo lysis. Toxic activity is neutralized by coexpression of the cognate immunity protein Tri1-Sp; Tri1-Sp neutralizes this protein both by binding to and occluding the active site (via Tri1's N-terminal extension) and by hydrolysis of the ADP-ribosyl moiety from the target protein. Tre1 can also be neutralized by non-cognate immunity protein Tri1-Pp from P.putida strain GB-1, with which it does not form a stable complex; DraG of R.palustris does not neutralize the toxic effects of this protein. In interbacterial competition studies Tri1 from P.putida strain B6-2 also neutralizes this protein. L-arginyl-[protein] + NAD(+) = H(+) + N(omega)-(ADP-D-ribosyl)-L-arginyl-[protein] + nicotinamide Forms a stable complex with cognate immunity protein Tri1-Sp. Probably delivered to target cells by a type 6 secretion system (T6SS). The ART domain is toxic when expressed as a protein fragment. A double tre1-tri1 deletion is outcompeted by wild-type cells, but not by wild-type cells missing a type 6 secretion system (T6SS). Belongs to the Arg-specific ADP-ribosyltransferase family.