Structural aspects of nucleotide ligand binding by a bacterial 2H phosphoesterase

Myllykoski, Matti; Kursula, Petri

The 2H phosphoesterase superfamily is an ancient group of proteins and protein domains characterized by a common fold and a few conserved active site residues [1, 2] . Various catalytic activities have been assigned for the 2H enzymes: hydrolysis of a 2 0 ,3 0 -cyclic phosphate, in either nucleotides or 3 0 -ends of RNA molecules, into 2 0 -phosphate [3] [4] [5] , hydrolysis of ADPribose 1 00 ,2 00 -cyclic phosphates into ADP-ribose 1 00 -phosphate [6] [7] [8] , generation and/or cleavage of 2 0 -5 0 -linkages between nucleotides or RNA molecules, such as tRNA halves [3, [9] [10] [11] [12] [13] , and 3 0 -5 0 exonucleolytic removal of terminal uridine nucleotides from snRNA with the simultaneous generation of 2 0 ,3 0 -cyclic phosphates at the terminus [14] . The structurally best-a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 characterized 2H enzyme is the mammalian myelin enzyme 2 0 ,3 0 -cyclic nucleotide 3 0 -phosphodiesterase (CNPase) [15] [16] [17] [18] [19] , but even for this enzyme, the biological function remains enigmatic [5] .