Expression and comparative analysis of recombinant rat and mouse RT6 T cell mono(ADP-ribosyl)transferases in E. coli

Recombinant RT6 proteins of rat and mouse were analyzed for NAD-metabolizing, i.e. mono(ADP-ribosyl)transferase, NAD-glycohydrolase (NADase) and ADP-ribosyl cyclase activities. The results reveal surprising intra- as well as inter-species differences in enzyme activities. While mouse Rt6 proteins were found to be strong arginine-specific transferases, but comparatively weak NADases, the opposite held true for rat RT6, for which transferase activity could only be detected in the form of arginine-specific auto-ADP-ribosylation, displayed by RT6.2 but not by RT6.1. NADase activity of rat RT6 was not accompanied by production of cyclic ADPR (cADPR). Rat RT6 gained potent arginine-specific transferase activity by exchange of a single amino acid for the corresponding residue of the mouse proteins.