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Pyrimidine Biosynthesis (pyrimidine + biosynthesis)

Distribution by Scientific Domains

Chemistry	60%

Selected Abstracts

A Caenorhabditis elegans model of orotic aciduria reveals enlarged lysosome-related organelles in embryos lacking umps-1 function

FEBS JOURNAL, Issue 6 2010
Steven Levitte
Gut granules are cell type-specific lysosome-related organelles found within the intestinal cells of Caenorhabditis elegans. To investigate the regulation of lysosome-related organelle size, we screened for C. elegans mutants with substantially enlarged gut granules, identifying alleles of the vacuolar-type H+ -ATPase and uridine-5,-monophosphate synthase (UMPS)-1. UMPS-1 catalyzes the conversion of orotic acid to UMP; this comprises the two terminal steps in de novo pyrimidine biosynthesis. Mutations in the orthologous human gene UMPS result in the rare genetic disease orotic aciduria. The umps-1(,) mutation promoted the enlargement of gut granules to 250 times their normal size, whereas other endolysosomal organelles were not similarly affected. UMPS-1::green fluorescent protein was expressed in embryonic and adult intestinal cells, where it was cytoplasmically localized and not obviously associated with gut granules. Whereas the umps-1(,) mutant is viable, combination of umps-1(,) with mutations disrupting gut granule biogenesis resulted in synthetic lethality. The effects of mutations in pyr-1, which encodes the enzyme catalyzing the first three steps of de novo pyrimidine biosynthesis, did not phenotypically resemble those of umps-1(,); instead, the synthetic lethality and enlargement of gut granules exhibited by the umps-1(,) mutant was suppressed by pyr-1(,). In a search for factors that mediate the enlargement of gut granules in the umps-1(,) mutant, we identified WHT-2, an ABCG transporter previously implicated in gut granule function. Our data suggest that umps-1(,) leads to enlargement of gut granules through a build-up of orotic acid. WHT-2 possibly facilitates the increase in gut granule size of the umps-1(,) mutant by transporting orotic acid into the gut granule and promoting osmotically induced swelling of the compartment. [source]

Regulation of pyrimidine nucleotide formation in Pseudomonas reptilivora

LETTERS IN APPLIED MICROBIOLOGY, Issue 2 2004
T.P. West
Abstract Aims:, To study the regulation of de novo pyrimidine biosynthesis in the pathogenic bacterium Pseudomonas reptilivora ATCC 14836. Methods and Results:, The pyrimidine biosynthetic pathway enzymes were assayed in extracts of Ps. reptilivora ATCC 14836 cells and of cells from an auxotroph lacking aspartate transcarbamoylase activity. Pyrimidine biosynthetic pathway enzyme activities in ATCC 14836 were influenced by the addition of pyrimidine bases to the culture medium with orotic acid addition inducing dihydroorotase activity. Pyrimidine starvation of the transcarbamoylase mutant strain increased its de novo enzyme activities suggesting that the de novo pathway was also subject to repression by a pyrimidine-related compound. Aspartate transcarbamoylase activity in ATCC 14836 was inhibited in vitro by pyrophosphate and ATP. Conclusions:, Regulation of pyrimidine biosynthesis in Ps. reptilivora was observed at the level of enzyme synthesis and at the level of activity for aspartate transcarbamoylase. Its regulation of enzyme synthesis seemed to be more highly controlled than what was observed in the related species Ps. fluorescens. Significance and Impact of the Study:, This investigation found that pyrimidine biosynthesis is controlled in Ps. reptilivora. This could prove helpful to future studies exploring its pathogenicity. [source]

Crystal structure of an enhancer of rudimentary homolog (ERH) at 2.1 Å resolution

PROTEIN SCIENCE, Issue 7 2005
Ryoichi Arai
Abstract The enhancer of rudimentary gene, e(r), of Drosophila melanogaster encodes an enhancer of rudimentary (ER) protein with functions implicated in pyrimidine biosynthesis and the cell cycle. The ER homolog (ERH) is highly conserved among vertebrates, invertebrates, and plants. Xenopus laevis ERH was reported to be a transcriptional repressor. Here we report the 2.1 Å crystal structure of murine ERH (Protein Data Bank ID 1WZ7), determined by the multiwavelength anomalous dispersion (MAD) method. The monomeric structure of ERH comprises a single domain consisting of three ,-helices and four ,-strands, which is a novel fold. In the crystal structure, ERH assumes a dimeric structure, through interactions between the ,-sheet regions. The formation of an ERH dimer is consistent with the results of analytical ultracentrifugation. The residues at the core region and at the dimer interface are highly conserved, suggesting the conservation of the dimer formation as well as the monomer fold. The long flexible loop (44,53) is also significantly conserved, suggesting that this loop region may be important for the functions of ERH. In addition, the putative phosphorylation sites are located at the start of the ,2-strand (Thr18) and at the start of the ,1-helix (Ser24), implying that the phosphorylation might cause some structural changes. [source]

Structure of pyrR (Rv1379) from Mycobacterium tuberculosis: a persistence gene and protein drug target

ACTA CRYSTALLOGRAPHICA SECTION D, Issue 4 2005
Katherine A. Kantardjieff
The Mycobacterium tuberculosis pyrR gene (Rv1379) encodes a protein that regulates the expression of pyrimidine-nucleotide biosynthesis (pyr) genes in a UMP-dependent manner. Because pyrimidine biosynthesis is an essential step in the progression of TB, the gene product pyrR is an attractive antitubercular drug target. The 1.9,Å native structure of Mtb pyrR determined by the TB Structural Genomics Consortium facilities in trigonal space group P3121 is reported, with unit-cell parameters a = 66.64, c = 154.72,Å at 120,K and two molecules in the asymmetric unit. The three-dimensional structure and residual uracil phosphoribosyltransferase activity point to a common PRTase ancestor for pyrR. However, while PRPP- and UMP-binding sites have been retained in Mtb pyrR, a distinct dimer interaction among subunits creates a deep positively charged cleft capable of binding pyr mRNA. In silico screening of pyrimidine-nucleoside analogs has revealed a number of potential lead compounds that, if bound to Mtb pyrR, could facilitate transcriptional attenuation, particularly cyclopentenyl nucleosides. [source]