Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.48 (transcriptase)
 9,479 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Strains of Escherichia coli causing enterohemorrhagic colitis belonging to the O157:H7 lineage are reported to be highly related. Fifteen strains of E. coli O157:H7 and 1 strain of E. coli O46:H(-) (nonflagellated) were examined for the presence of potassium tellurite resistance (Te(r)). Te(r) genes comprising terABCDEF were shown previously to be part of a pathogenicity island also containing integrase, phage, and urease genes. PCR analysis, both conventional and light cycler based, demonstrated that about one-half of the Te(r) E. coli O157:H7 strains (6 of 15), including the Sakai strain, which has been sequenced, carried a single copy of the Te(r) genes. Five of the strains, including EDL933, which has also been sequenced, contained two copies. Three other O157:H7 strains and the O46:H(-) strain did not contain the Te(r) genes. In strains containing two copies, the Te(r) genes were associated with the serW and serX tRNA genes. Five O157:H7 strains resembled the O157 Sakai strain whose sequence contained one copy, close to serX, whereas in one isolate the single copy was associated with serW. There was no correlation between Te(r) and the ability to produce Shiga toxin ST1 or ST2. The Te(r) MIC for most strains, containing either one or two copies, was 1,024 micro g/ml, although for a few the MIC was intermediate, 64 to 128 micro g/ml, which could be increased to 512 micro g/ml by pregrowth of strains in subinhibitory concentrations of potassium tellurite. Reverse transcriptase PCR analysis confirmed that in most strains Te(r) was constitutive but that in the rest it was inducible and involved induction of terB and terC genes. Only the terB, -C, -D, and -E genes are required for Te(r). The considerable degree of homology between the ter genes on IncH12 plasmid R478, which originated in Serratia marcescens, and pTE53, from an E. coli clinical isolate, suggests that the pathogenicity island was acquired from a plasmid. This work demonstrates diversity among E. coli O157:H7 isolates, at least as far as the presence of Te(r) genes is concerned.
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PMID:Genomic variability of O islands encoding tellurite resistance in enterohemorrhagic Escherichia coli O157:H7 isolates. 1216 92

Ureases are multisubunit enzymes requiring Ni(2+) for activity. The low pH-inducible urease gene cluster in Streptococcus salivarius 57.I is organized as an operon, beginning with ureI, followed by ureABC (structural genes), and ureEFGD (accessory genes). Urease biogenesis also requires a high-affinity Ni(2+) uptake system. By searching the partial genome sequence of a closely related organism, Streptococcus thermophilus LMG18311, three open reading frame (ORFs) homologous to those encoding proteins involved in cobalamin biosynthesis and cobalt transport (cbiMQO) were identified immediately 3' to the ure operon. To determine whether these genes were involved in urease biogenesis by catalyzing Ni(2+) uptake in S. salivarius, regions 3' to ureD were amplified by PCRs from S. salivarius by using primers identical to the S. thermophilus sequences. Sequence analysis of the products revealed three ORFs. Reverse transcriptase PCR was used to demonstrate that the ORFs are transcribed as part of the ure operon. Insertional inactivation of ORF1 with a polar kanamycin marker completely abolished urease activity and the ability to accumulate (63)Ni(2+) during growth. Supplementation of the growth medium with NiCl(2) at concentrations as low as 2.5 micro M partially restored urease activity in the mutant. Both wild-type and mutant strains showed enhanced urease activity when exogenous Ni(2+) was provided at neutral pH. Enhancement of urease activity by adding nickel was regulated at the posttranslational level. Thus, ORF1, ORF2, and ORF3 are part of the ure operon, and these genes, designated ureM, ureQ, and ureO, respectively, likely encode a Ni(2+)-specific ATP-binding cassette transporter.
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PMID:Identification and characterization of the nickel uptake system for urease biogenesis in Streptococcus salivarius 57.I. 1461 41