Phosphoribosyltransferase superfamily: A comparative structural analysis

Purine phosphoribosyltransferases are members of a group of enzymes that ar e responsible for the formation of purine, pyrimidine and pyridine nucleoti des. One feature of this family is a flexible loop, which is involved in th e catalytic mechanism. This loop is variable both in sequence and structure in the phosphoribosyltransferase family. This paper describes the modellin g and validation of a model of Plasmodium falciparum hypoxanthine-guanidine - phosphoribosyltransferase in an open conformation. A comparison of this m odel with 3D-structures of other members of the phosphorybosyl-transferase family has allowed an assessment of the role of the open and closed conform ations of the loop in the catalytic mechanism.