Characterization of active-site residues in diadenosine tetraphosphate hydrolase from Lupinus angustifolius

Abstract

Site-directed mutagenesis has been used to characterize the functions of key amino acid residues in the catalytic site of the 'nudix' hydrolase, (asymmetrical) diadenosine 5′,5‴-P1,P4-tetraphosphate (Ap4A) hydrolase (EC 3.6.1.17) from Lupinus angustifolius, the three-dimensional solution structure of which has recently been solved. Residues within the nudix motif, Gly-(Xaa)5-Glu-(Xaa)7-Arg-Glu-Uaa-Xaa-(Glu) 2-Xaa-Gly (where Xaa represents unspecified amino acids and Uaa represents the bulky aliphatic amino acids Ile, Leu or Val) conserved in 'nudix enzymes', and residues important for catalysis from elsewhere in the molecule, were mutated and the expressed proteins characterized. The results..