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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Urea is an important nitrogen source for many microorganisms, but urea active transporters have not been characterized at a molecular level in any bacterium. Cells of Synechocystis sp. PCC 6803 and Anabaena sp. PCC 7120 exhibited the capacity to take up [14C]-urea from low-concentration (<1 microM) urea solutions. The Ks of Anabaena cells for urea was about 0.11 microM, and the observed uptake activity involved the transport and metabolism of urea. In contrast to urease, which was constitutively ex-pressed, expression of the high-affinity urea uptake activity was subjected to nitrogen control. In an Anabaena ureG (urease-) mutant, a concentrative, active transport of urea could be demonstrated. We found that a mutant of open reading frame (ORF) sll0374 from the Synechocystis genomic sequence lacked urea transport activity. This ORF encoded a conserved component of an ABC-type transporter, but it is not clustered together with any other possible transporter-encoding gene. An Anabaena homologue of sll0374, urtE, was isolated and found to be part of a cluster of genes, urtABCDE, putatively encoding all the elements of an ABC-type permease. Although the longest transcript that we could detect only covered urtABC, the impairment of urea transport by inactivation of urtA, urtB or urtE suggested that the whole gene cluster is expressed producing the urea permease. Expression was induced under nitrogen-limiting conditions, and a complex promoter regulated by the cyanobacterial global nitrogen control transcription factor NtcA was found upstream from urtA. Our work adds urea to the known substrates of the versatile class of ABC-type transporters and suggests the involvement of a transporter of this superfamily in urea scavenging by some bacteria in natural environments.
Mol Microbiol 2002 Feb
PMID:An ABC-type, high-affinity urea permease identified in cyanobacteria. 1192 26

Human renal dipeptidase is a membrane-bound glycoprotein hydrolyzing dipeptides and is involved in hydrolytic metabolism of penem and carbapenem beta-lactam antibiotics. The crystal structures of the saccharide-trimmed enzyme are determined as unliganded and inhibitor-liganded forms. They are informative for designing new antibiotics that are not hydrolyzed by this enzyme. The active site in each of the (alpha/beta)(8) barrel subunits of the homodimeric molecule is composed of binuclear zinc ions bridged by the Glu125 side-chain located at the bottom of the barrel, and it faces toward the microvillar membrane of a kidney tubule. A dipeptidyl moiety of the therapeutically used cilastatin inhibitor is fully accommodated in the active-site pocket, which is small enough for precise recognition of dipeptide substrates. The barrel and active-site architectures utilizing catalytic metal ions exhibit unexpected similarities to those of the murine adenosine deaminase and the catalytic domain of the bacterial urease.
J Mol Biol 2002 Aug 09
PMID:Crystal structure of human renal dipeptidase involved in beta-lactam hydrolysis. 1214 77

Urea uptake in eukaryotes and prokaryotes occurs via diffusion or active transport across the cell membrane. Facilitated diffusion of urea in both types of organisms requires a single-component channel. In bacteria, these transport systems allow rapid access of urease to its substrate, resulting in ammonia production, which is needed either for resistance to acidity or as a nitrogen source. In Yersinia pseudotuberculosis, a ureolytic enteropathogenic bacterium, a gene of unknown function (yut) located near the urease locus was found to encode a putative membrane protein with weak homology to single-component eukaryotic urea transporters. When expressed in Xenopus oocytes, Yut greatly increases cellular permeability to urea. Inactivation of yut in Y. pseudotuberculosis results in diminished apparent urease activity and reduced resistance to acidity in vitro when urea is present in the medium. In the mouse model, bacterial colonization of the intestine mucosa is delayed with the Yut-deficient mutant. Although structurally unrelated, Yut and the Helicobacter pylori UreI urea channel were shown to be functionally interchangeable in vitro and are sufficient to allow urea uptake in both bacteria, thereby confirming their function in the respective parent organisms. Homologues of Yut were found in other yersiniae, Actinobacillus pleuropneumoniae, Brucella melitensis, Pseudomonas aeruginosa and Staphylococcus aureus. The Y. pseudotuberculosis Yut protein is therefore the first member of a novel class of bacterial urea permeases related to eukaryotic transporters.
Mol Microbiol 2002 Aug
PMID:The Yersinia pseudotuberculosis Yut protein, a new type of urea transporter homologous to eukaryotic channels and functionally interchangeable in vitro with the Helicobacter pylori UreI protein. 1218 Sep 33

Urease from seeds of pigeonpea showed a time-dependent and irreversible inactivation at very low concentrations of heavy metal ions. Concentration of Cu(2+), Hg(2+) and Ag(+) required for 50% inactivation, on 10 min of incubation, were found to be 2.2 x 10(-6), 2.9 x 10(-8) and 6.3 x 10(-12) M, respectively. The kinetics of inactivation with each of these metal ions was found to be biphasic, with half of the activity being lost in a fast phase and remaining in a slow phase. Acetohydroxamate (AHA) inhibits pigeonpea urease competitively and reversibly with a K(i) of 0.041 mM at pH 7.3. This inhibition was found to be pH dependent. A reversible and time-dependent inhibition was observed with AHA. AHA inhibition revealed biphasic kinetics as observed with the heavy metal ions. Pigeonpea urease was also inhibited by fluoride ions competitively with a K(i) value of 1.23 mM. These inhibition studies suggest the possible interaction of these inhibitors with active site thiol groups and Ni (II) ion. A mechanism has been proposed for each of these inhibitors and compared with inhibition studies reported for other ureases.
J Biochem Mol Biol Biophys 2002 Feb
PMID:Kinetics of inhibition and molecular asymmetry in pigeonpea (Cajanus cajan) urease. 1218 75

Plant orthologs of the bacterial urease accessory genes ureD and ureF, which are required for the insertion of the nickel ion at the active site, have been isolated from soybean ( Glycine max L. Merr.), tomato ( Lycopersicon esculentum) and Arabidopsis thaliana. The functionality of soybean UreD and UreF was tested by measuring their ability to complement urease-negative mutants of Schizosaccharomyces pombe, a eukaryote which produces a "plant-like" urease of ~90 kDa. The S. pombe ure4 mutant was complemented by a 12-kb fragment of S. pombe genomic DNA, which was shown by PCR to contain a putative ureD gene. However, ure4 was not complemented by a UreD cDNA soybean, expressed under the control of a strong promoter. In contrast, an S. pombe ure3 mutation was complemented by both a 10-kb fragment of S. pombe DNA containing ureF and the UreF cDNA from soybean. Soybean Eu2 is a candidate urease accessory gene; its product cooperates with the Eu3 protein in activating apourease in vitro. However, the sequences of UreD and UreF transcripts from two eu2/eu2 mutants, recovered as RT-PCR products, revealed no mutational alteration, suggesting that Eu2 encodes neither UreD nor UreF.
Mol Genet Genomics 2002 Dec
PMID:Activation of the urease of Schizosaccharomyces pombe by the UreF accessory protein from soybean. 1247 50

The pathogenic yeast Cryptococcus neoformans (Cn) var. gattii causes meningoencephalitis in healthy individuals, unlike the better known Cn varieties grubii and neoformans, which are common in immunocompromised individuals. The virulence determinants and mechanisms of host predilection are poorly defined for var. gattii. The present study focused on the characterization of a Cu,Zn superoxide dismutase (SOD1) gene knock-out mutant constructed by developing a DNA transformation system. The sod1 mutant was highly sensitive to the redox cycling agent menadione, and showed fragmentation of the large vacuole in the cytoplasm, but no other defects were seen in growth, capsule synthesis, mating, sporulation, stationary phase survival or auxotrophies for sulphur-containing amino acids. The sod1 mutant was markedly attenuated in virulence in a mouse model, and it was significantly susceptible to in vitro killing by human neutrophils (PMNs). The deletion of SOD1 also resulted in defects in the expression of a number of virulence factors, i.e. laccase, urease and phospholipase. Complementation of the sod1 mutant with SOD1 resulted in recovery of virulence factor expression and menadione resistance, and in restoration of virulence. Overall, these results suggest that the antioxidant function of Cu,Zn SOD is critical for the pathogenesis of the fungus, but is dispensable in its saprobic life. This report constitutes the first instance in which superoxide dismutase has been directly implicated in the virulence of a fungal pathogen.
Mol Microbiol 2003 Mar
PMID:Characterization of Cu,Zn superoxide dismutase (SOD1) gene knock-out mutant of Cryptococcus neoformans var. gattii: role in biology and virulence. 1262 21

Comparative physiological studies are a powerful tool for revealing common animal adaptations. Amino acid catabolism produces ammonia which is detoxified through the synthesis of urea (mammals, some fish), uric acid (birds), or urea and uric acid (reptiles). In mammalian herbivores and omnivores, urea nitrogen is salvaged by a series of steps involving urea transfer into the intestine, microbial mediated urea hydrolysis with synthesis of amino acids utilizing the liberated ammonia and transfer of the amino acids back to the host. A similar series of steps occur in omnivorous/granivorous and herbivorous birds, although in this case urine, containing uric acid, is refluxed directly into the intestine where microbes degrade the uric acid and utilize the liberated ammonia for amino acid synthesis. These amino acids are transferred back to the host. In reptiles and ureotelic fish not all of these steps have been experimentally confirmed. Reptiles like birds, reflux urine into the intestine where it is exposed to the microflora. However, the capacity of these microbes to breakdown the uric acid and urea and utilize ammonia for amino acid synthesis has not been documented. Ureotelic fish transfer urea into the intestine where urease (presumably of bacterial origin) hydrolyzes the urea. However, the amino acid synthesizing capacity of the intestinal microflora has not been studied. The series of steps, as outlined, would define the prevailing nitrogen conservation system for herbivores and omnivores at least. However, it would appear that some animals, in particular the fruit-eating bat and perhaps the fruit-eating bird, may have evolved alternative, as yet uncharacterized, adaptations to a very limited nitrogen intake.
Comp Biochem Physiol B Biochem Mol Biol 2003 Apr
PMID:Do mammals, birds, reptiles and fish have similar nitrogen conserving systems? 1267 Jul 82

Soybean (Glycine max [L.] Merrill) mutant aj6 carries a single recessive lesion, aj6, that eliminates ubiquitous urease activity in leaves and callus while retaining normal embryo-specific urease activity. Consistently, aj6/aj6 plants accumulated urea in leaves. In crosses of aj6/aj6 by urease mutants at the Eu1, Eu2, and Eu3 loci, F(1) individuals exhibited wild-type leaf urease activity, and the F(2) segregated urease-negative individuals, demonstrating that aj6 is not an allele at these loci. F(2) of aj6/aj6 crossed with a null mutant lacking the Eu1-encoded embryo-specific urease showed that ubiquitous urease was also inactive in seeds of aj6/aj6. The cross of aj6/aj6 to eu4/eu4, a mutant previously assigned to the ubiquitous urease structural gene (R.S. Torisky, J.D. Griffin, R.L. Yenofsky, J.C. Polacco [1994] Mol Gen Genet 242: 404-414), yielded an F(1) having 22% +/- 11% of wild-type leaf urease activity. Coding sequences for ubiquitous urease were cloned by reverse transcriptase-polymerase chain reaction from wild-type, aj6/aj6, and eu4/eu4 leaf RNA. The ubiquitous urease had an 837-amino acid open reading frame (ORF), 87% identical to the embryo-specific urease. The aj6/aj6 ORF showed an R201C change that cosegregated with the lack of leaf urease activity in a cross against a urease-positive line, whereas the eu4/eu4 ORF showed a G468E change. Heteroallelic interaction in F(2) progeny of aj6/aj6 x eu4/eu4 resulted in partially restored leaf urease activity. These results confirm that aj6/aj6 and eu4/eu4 are mutants affected in the ubiquitous urease structural gene. They also indicate that radical amino acid changes in distinct domains can be partially compensated in the urease heterotrimer.
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PMID:Interallelic complementation at the ubiquitous urease coding locus of soybean. 1291 38

Ureaplasma urealyticum is a common inhabitant of mucosal surfaces but is also associated with a higher incidence of pneumonia and bronchopulmonary dysplasia in preterm infants. Culture and polymerase chain reaction demonstrate high isolation rates of ureaplasma in clinical specimens documenting their presence but do not associate the organism directly with the diseased tissue. In this study, lung tissue samples from newborn mice inoculated intranasally with U. urealyticum were used to develop an in situ hybridization (ISH) test for the organism. In situ hybridization allows the localization of gene expression for visualization within the context of tissue morphology. New techniques which use biotinyl-tyramide based signal amplification have been able to greatly enhance the sensitivity of ISH. Using the Dako GenPoint Catalyzed Signal Amplification system to detect a biotinylated DNA probe specific for an internal nucleotide sequence within the urease gene of U. urealyticum, the organism was detected within the infected murine lung tissues. Electron microscopy was used to verify the presence of the organisms in the positive ISH areas. The ISH procedure developed in this study can be used to analyze the presence of ureaplasma in human neonatal lung tissue with the corresponding histopathology.
Exp Mol Pathol 2003 Oct
PMID:Ureaplasma in lung. 1. Localization by in situ hybridization in a mouse model. 1451 80

The carbon-14 urea breath test (UBT) is a reliable and non-invasive technique for the diagnosis of Helicobacter pylori (HP) infection. In this study we evaluated the diagnostic performance of a new, practical and low-dose (14)C-UBT system for the diagnosis of HP and compared the results with those obtained using the standard method. Seventy-five patients (56 female, 19 male) with dyspepsia underwent (14)C-UBT and endoscopy with antral biopsies for histological analysis. The rapid urease test (CLO test) was applied to 50 of these patients. After a 6-h fasting period, a 37-kBq (14)C-urea capsule was swallowed for UBT. Breath samples were collected and counted using two different methods, the Heliprobe method and the standard method. In the Heliprobe method, patients exhaled into a special dry cartridge system (Heliprobe BreathCard) at 10 min. The activities of the cartridges were counted using a designated small GM counter system (Heliprobe analyser). Results were expressed both as counts per minute (HCPM) and as grade (0, not infected; 1, equivocal; 2, infected) according to the counts. In the standard method, breath samples were collected by trapping in a liquid CO(2) absorber. Radioactivity was counted as disintegrations per minute (SDPM) using a liquid scintillation counter after addition of a liquid scintillation cocktail. Histological examination was used as a gold standard. Two patients were excluded from the study because of inadequate biopsy sampling. Forty-eight patients (65%) were found to be HP positive on histology. The Heliprobe method correctly classified 48 of 48 HP-positive patients and 19 of 25 HP-negative patients (sensitivity 100%, specificity 76%, PPV 88%, NPV 100%, accuracy 91%). The standard method correctly classified 48 of 48 HP-positive patients and 20 of 25 HP-negative patients (sensitivity 100%, specificity 80%, PPV 90%, NPV 100%, accuracy 93%). On the other hand, the CLO test identified 26 of 32 HP-positive and 12 of 16 HP-negative patients (sensitivity 81%, specificity 75%, PPV 86%, NPV 66%, accuracy 79%). With the Heliprobe method, all of the positive results were grade 2, and all of the negative results were grade 0. No patients were defined as having grade 1 results. Counts allowed clear discrimination of HP-positive and -negative patients with both methods, the difference being statistically significant in each case ( P<0.001). A significant correlation was found between HCPM and SDPM ( r 0.863, P<0.001). According to the ROC analysis, the area under the curve was nearly the same with HCPM (AUC, 0.888; 95% CI, 0.785-0.992) and SDPM (AUC, 0.898; 95% CI, 0.802-0.994). In conclusion, the new (14)C-UBT system is a highly accurate method for the diagnosis of HP infection. It is rapid and practical, and therefore suitable for clinical and office practice.
Eur J Nucl Med Mol Imaging 2003 Nov
PMID:A new, practical, low-dose 14C-urea breath test for the diagnosis of Helicobacter pylori infection: clinical validation and comparison with the standard method. 1457 83


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