IDENTIFICATION AND CHARACTERIZATION OF THE NUDIX HYDROLASE FROM THE ARCHAEON, METHANOCOCCUS-JANNASCHII, AS A HIGHLY SPECIFIC ADP-RIBOSE PYROPHOSPHATASE

The MJ1149 gene from the Archaeon, Methanococcus jannaschii, has been cloned and expressed in Escherichia coli, The 19-kDa protein containin g the Nudix box, GX(5)EX(7)REUXEEXGU, has been purified and identified as a highly specific enzyme catalyzing the Mg2+-dependent hydrolysis of ADP-ribose according to the equation: ADP-ribose + H2O --> AMP + ri bose-5-phosphate. The enzyme retains full activity when heated to 80 d egrees C, and the rate of hydrolysis is 15-fold higher at 75 degrees C than at 37 degrees C in keeping with the thermophilicity of the organ ism. This is the first Nudix hydrolase identified from the Archaea, in dicating that the family of enzymes containing the Nudix signature seq uence is represented in all three kingdoms.