Nidulans Phosphoribosyl Pyrophosphate Synthetase (PRS) Function Of The Biological Family And Synergistic Effects On The Regulation Of Enzyme Activity

Phosphoribosyl pyrophosphate synthetase (PRS—EC:2.7.6.1) catalyses the reaction of ribose-5-phosphate and adenine ribonucleotide triphosphate(ATP) with the formation of5-phosphoribosyl-a-l-pyrophosphate (PRPP) and adenine ribonucleotide monophosphate (AMP). The PRS reaction product, PRPP, is used in many different pathways such as the pentose phosphate pathway, the de novo and salvage purine and pyrimidine nucleotide pathways, and the biosynthesis of nucleotide coenzymes, histidine and tryptophane amino acids. In human beings, Missense mutations in HumanPRPS1has related to many hereditary diseases, such as Arts syndrome and X-linked nonsyndromic sensorineural deafness.Aseprgillus nidulans is a multi-celluar eukaryotic organism, unlike to the unicelluar yeast, it’s more related to human beings. A. nidulans also has a well-established gene manipulation and celluar development analysis system, makes it an excelllent model organism to study the biological functions of human diseases related genes.By homologus blast, we found that there exist three homologus PRS proteins in A. nidulans. Based on the homologus relationship with PRS1-5in budding yeast Saccharomyces cerevisiae, we desiganated three PRS proteins in A. nidulans as AnPRS1(AN6711.4), AnPRS2(AN1965.4) and AnPRS3(AN3169.4). Among those, AnPRS2shares the highest identity(66.7%) with human diseases related protein HumanPRPS1, and AnPRS2also cotains all the mutation sites that related to diseases in HumanPRPS1.By gene knock out and promoter replacement experiment, we found in A. nidulans, deletion or inhibit expression of Anprsl doesn’t exert to much influence on the hyphal growth and develepment. However, deletion or inhibit expression of either Anprs2or Anprs3would induce germination faliure, exhibit phenotypes of lethal genes. Further analysis suggests AnPRS2is also essential during the hyphal enlongation, while down regulation of AnPRS1or AnPRS2can be tolerated in the hyphal enlongation process. Conditional strains are used to over express AnPRS1,2,3. And we found, over expression of AnPRS2would induce septation and conidiation faliure, in adition, over expression of AnPRS1and AnPRS3also induce septation and conidiation defects in some extent.To understand why AnPRS1,2,3has different biological functions, we assessed the changes of PRS enzyme activity under standard protocols when expression of AnPRS1,2,3had been inhibited. We found the contributions of AnPRS1,2,3to PRS enzyme activity are differentiated, when repressed AnPRS2, the enzyme activity is only5%to the wild type, AnPRS3is25%and AnPRS1is80%. Real-time qPCR results suggested the transcription level of Anprsl,2,3during the strain develeoment are also differentiated, with Anprs2is the highest, Anprsl and Anprs3are relatively low.To sum up, AnPRS2as a homologus protein to human diseases related protein HumanPRPS1, also play important roles during spores germination, cytokinesis and hyphal enlongation in Aspergillus nidulans, our study will help to undertand the molecular and cell biology mechanism behind the missense mutation of HumanPRPS1induced human diseases.