Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:6.3.4.6 (urease)
 7,490 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Four microbial enzymes are known to require nickel: hydrogenase, methyl coenzyme M reductase, carbon monoxide dehydrogenase, and urease. Recent biochemical and molecular biological experiments have provided clear evidence for the existence of multiple auxiliary genes that facilitate nickel incorporation into urease and hydrogenase. Similarly, accessory factors are also likely to be required for the other two enzymes. One of the urease-related genes (ureE) encodes a cytoplasmic protein that has been purified and shown to bind nickel reversibly. We propose that the UreE protein serves as a nickel donor to urease apoprotein. A second urease-related auxiliary gene (ureG) possesses a sequence motif that is found in ATP- and GTP-binding proteins. We have shown that nickel incorporation into urease requires energy and speculate that the UreG protein may serve as an energy transducer, coupling the energy of NTP hydrolysis to metallocenter incorporation. The UreG protein is related in sequence to HypB, a protein that has been proposed to function in nickel processing in hydrogenases. Hence, the mechanisms for metallocenter biosynthesis in these two dissimilar enzymes may have evolved from a common nickel incorporation system.
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PMID:Nickel enzymes in microbes. 802 91

The Klebsiella aerogenes ureE gene product was previously shown to facilitate assembly of the urease metallocenter (Lee, M.H., et al., 1992, J. Bacteriol. 174, 4324-4330). UreE protein has now been purified and characterized. Although it behaves as a soluble protein, UreE is predicted to possess an amphipathic beta-strand and exhibits unusually tight binding to phenyl-Sepharose resin. Immunogold electron microscopic studies confirm that UreE is a cytoplasmic protein. Each dimeric UreE molecule (M(r) = 35,000) binds 6.05 + 0.25 nickel ions (Kd of 9.6 +/- 1.3 microM) with high specificity according to equilibrium dialysis measurements. The nickel site in UreE was probed by X-ray absorption and variable-temperature magnetic circular dichroism spectroscopies. The data are most consistent with the presence of Ni(II) in pseudo-octahedral geometry with 3-5 histidyl imidazole ligands. The remaining ligands are nitrogen or oxygen donors. UreE apoprotein has been crystallized and analyzed by X-ray diffraction methods. Addition of nickel ion to apoprotein crystals leads to the development of fractures, consistent with a conformational change upon binding nickel ion. We hypothesize that UreE binds intracellular nickel ion and functions as a nickel donor during metallocenter assembly into the urease apoprotein.
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PMID:Purification and characterization of Klebsiella aerogenes UreE protein: a nickel-binding protein that functions in urease metallocenter assembly. 831 89

We investigated whether Helicobacter pylori cells actively secrete proteins such as the urease subunits UreA and UreB and the GroES and GroEL homologs HspA and HspB or whether these proteins were present in the extracellular compartment as a consequence of autolysis. Using a subcellular fractionation approach associated with quantitative Western blot analyses, we showed that the supernatant protein profiles were very different from those of the cell pellets, even for bacteria harvested in the late growth phase; this suggests that the release process is selective. A typical cytoplasmic protein, a beta-galactosidase homolog, was found exclusively associated with the pellet of whole-cell extracts, and no traces were found in the supernatant. In contrast, UreA, UreB, HspA, and HspB were mostly found in the pellet but significant amounts were also present in the supernatant. HspA and UreB were released into the supernatant at the same rate throughout the growth phase (3%), whereas large portions of HspB and UreA were released during the stationary phase (over 30 and 20%, respectively) rather than during the early growth phase (20% and 6, respectively). The profiles of protein obtained after water extraction of the bacteria with those of the proteins naturally released within the liquid culture supernatants demonstrated that water extraction led to the release of a large amount of protein due to artifactual lysis. Our data support the conclusion that a specific and selective mechanism(s) is involved in the secretion of some H. pylori antigens. A programmed autolysis process does not seem to make a major contribution.
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PMID:Evidence for specific secretion rather than autolysis in the release of some Helicobacter pylori proteins. 948 91

The molecular identification of the Corynebacterium glutamicum urea uptake system is described. This ABC-type transporter is encoded by the urtABCDE operon, which is transcribed in response to nitrogen limitation. Expression of the urt genes is regulated by the global nitrogen regulator AmtR, and an amtR deletion strain showed constitutive expression of the urtABCDE genes. The AmtR repressor protein also controls transcription of the urease-encoding ureABCEFGD genes in C. glutamicum. The ure gene cluster forms an operon which is mainly transcribed in response to nitrogen starvation. To confirm the increased synthesis of urease subunits under nitrogen limitation, proteome analyses of cytoplasmic protein extracts from cells grown under nitrogen surplus and nitrogen limitation were carried out, and five of the seven urease subunits were identified.
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PMID:Molecular identification of the urea uptake system and transcriptional analysis of urea transporter- and urease-encoding genes in Corynebacterium glutamicum. 1551 78

Kinetoplastids encode a single nuclear tryptophanyl tRNA that contains a CCA anticodon able to decode the UGG codons used in cytoplasmic protein synthesis but cannot decode the mitochondrial UGA codons. Following mitochondrial import, this problem is circumvented in Trypanosoma brucei by specifically editing the tRNA(Trp) anticodon to UCA, which can now decode the predominant mitochondrial UGA tryptophan codons. This tRNA also undergoes an unusual thiolation at position 33 of the anticodon loop, the only known modification at U33 in any tRNA. In other organisms, tRNA thiolation is mediated by the cysteine desulfurase, Nfs1 (IscS). However, T. brucei encodes two Nfs homologues, one cytoplasmic and the other mitochondrial. We show by a combination of RNA interference and Northern and Western analyses that the mitochondria-targeted TbNfs, and not TbNfs-like protein, is essential for thiolation of both cytosolic and mitochondrial tRNAs. Given the exclusive mitochondrial localization of TbNfs, how it mediates thiolation in the cytoplasm remains unclear. Furthermore, thiolation specifically affects thiolated tRNA stability in the cytoplasm but more surprisingly acts as a negative determinant for the essential C to U editing in T. brucei. This provides a first line of evidence for mitochondrial C to U editing regulation in this system.
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PMID:Thiolation controls cytoplasmic tRNA stability and acts as a negative determinant for tRNA editing in mitochondria. 1957 16