InterPro: IPR000836 Phosphoribosyltransferase

The name PRT comes from phosphoribosyltransferase (PRTase) enzymes, which carry out phosphoryl transfer reactions on 5-phosphoribosyl-alpha1-pyrophosphate PRPP, an activated form of ribose-5-phosphate. Members of Phosphoribosyltransferase (PRT) are catalytic and are regulatory proteins involved in nucleotide synthesis and salvage [1]. This includes a range of diverse phosphoribosyl transferase enzymes including adenine phosphoribosyltransferase (EC:2.4.2.7); hypoxanthine-guanine-xanthine phosphoribosyltransferase; hypoxanthine phosphoribosyltransferase (EC:2.4.2.8); ribose-phosphate pyrophosphokinase (EC:2.7.6.1); amidophosphoribosyltransferase (EC:2.4.2.14); orotate phosphoribosyltransferase (EC:2.4.2.10);uracil phosphoribosyltransferase (EC:2.4.2.9); and xanthine-guanine phosphoribosyltransferase (EC:2.4.2.22).

Not all PRT proteins are enzymes. For example, in some bacteria PRT proteins regulate the expression of purine and pyrimidine synthetic genes.

Members of PRT are defined by the protein fold and by a short 13-residue sequence motif, The motif consists of four hydrophobic amino acids, two acidic amino acids and seven amino acids of variable character, usually including glycine and threonine. The motif has been predicted to be a PRPP-binding site in advance of structural information [2, 3]. Apart of this motif, different PRT proteins have a low level of sequence identity, less than 15%. The PRT sequence motif is only found in PRTases from the nucleotide synthesis and salvage pathways. Other PRTases, from the tryptophan, histidine and nicotinamide synthetic and salvage pathways, lack the PRT sequence motif and appear to be unrelated to each other and unrelated to the PRT family.