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

Superoxide dismutase (SOD) activity was determined in the cell lysate of the axenically cultured Entamoeba histolytica isolate HM-1:IMSS. Under anaerobic culture conditions, 18.7 (+/- 4.9) units SOD activity (mg protein)-1 were found. By inhibition studies the activity was attributed to an iron-containing type of SOD (FeSOD). Using degenerate oligonucleotide primers derived from regions highly conserved in prokaryotic FeSOD sequences, a genomic DNA fragment was amplified by the polymerase chain reaction. The fragment was used to isolate FeSOD specific cDNA clones from a pathogenic and a nonpathogenic E. histolytica isolate. A comparison of the 2 sequences revealed 5% nucleotide differences resulting in a single amino acid exchange. The primary structure showed the characteristics of an iron-containing type of SOD with a homology of approximately 55% with other FeSOD sequences. The enzyme was found to be encoded by single copy genes in both the pathogenic and the nonpathogenic E. histolytica, but restriction fragment lengths differed between the 2 groups. In 5 isolates studied, no correlation was found between pathogenic behavior of the amebae and the expression of FeSOD-related mRNA.
Mol Biochem Parasitol 1991 Nov
PMID:Pathogenic and nonpathogenic Entamoeba histolytica: identification and molecular cloning of an iron-containing superoxide dismutase. 177 59

This review is concerned with the effects of environmental perturbations on the expression of the two superoxide dismutase (SOD) genes in Escherichia coli (sodA, MnSOD; sodB, FeSOD). Early studies using SOD activity, showed that MnSOD levels respond to changes in oxygen tension, type of substrate, redox active compounds, iron concentration, the nature of the terminal oxidant, and the redox potential of the medium. FeSOD levels appeared nominally insensitive to these perturbations. More recent molecular genetic studies revealed that sodA expression is subject to regulation by three major regulatory systems: fur (ferric uptake regulation) and arcA arcB (aerobic respiratory control) mediate repression of sodA, while a relatively new system, soxR soxS (superoxide response), mediates activation of sodA expression. By contrast, sodB expression, which is much less studied at this time, appears to be positively activated in trans by fur. A rudimentary gene regulation model is presented which rationalizes past observations, is experimentally testable, and should serve as a guide to future research in this area.
Mol Microbiol 1991 Nov
PMID:Regulation of sod genes in Escherichia coli: relevance to superoxide dismutase function. 177 51

A multicopy plasmid containing the Escherichia coli fur gene was introduced into Pseudomonas aeruginosa strain PA103C. This strain contains a toxA-lacZ fusion integrated into its chromosome at the toxA locus. Beta-galactosidase synthesis in this strain is regulated by iron, as is seen for exotoxin A production. Beta-galactosidase synthesis and exotoxin A production in PA103C containing multiple copies of E. coli fur was still repressed in low iron conditions. The transcription of regA, a positive regulator of toxA, was also found to be inhibited by multiple copies of the E. coli fur gene. In addition, the ability of PA103C containing multiple copies of E. coli fur to produce protease was greatly reduced relative to PA103C containing a vector control. A polyclonal rabbit serum containing antibodies that recognize E. coli Fur was used to screen whole-cell extracts from Vibrio cholerae, Shigella flexneri, Salmonella typhimurium and Pseudomonas aeruginosa. All strains tested expressed a protein that was specifically recognized by the anti-Fur serum. These results and those described above suggest that Fur structure and function are conserved in a variety of distinct bacterial genera and that at least some of these different genera use this regulatory protein to control genes encoding virulence factors.
Mol Microbiol 1991 Nov
PMID:Regulation of toxA and regA by the Escherichia coli fur gene and identification of a Fur homologue in Pseudomonas aeruginosa PA103 and PA01. 177 68

Twenty of the twenty-two MudII1734 insertions impairing the chrysobactin iron-assimilation system of Erwinia chrysanthemi 3937 were localized to a 50 kbp genomic insert contained in the R-prime plasmid, R'4 (Enard et al., 1988). Using the conjugative plasmid pULB110 (RP4::mini-Mu) and the generalized transducing phage phi EC2, we located this iron-transport region and the two unlinked mutations on the chromosome linkage map. Chrysobactin is a catechol-type siderophore and, as we have previously observed with the entA locus of Escherichia coli, the E. chrysanthemi-derived R'4 was found to complement E. coli entB and entE mutations. A 2.9 kb EcoRi and a 4.8 kb BamHI fragment in the R'4 sharing homology with the E. coli entCEBAP15 operon DNA were subcloned. These fragments were used as DNA/DNA hybridization probes to screen a wild-type gene library, yielding a recombinant cosmid (pEC7) able to complement mutations disrupting the 2,3-dihydroxybenzoic acid biosynthetic pathway in both Erwinia and Escherichia spp. as well as the E. coli entE mutation. Physical mapping of the genomic MudII1734 insertions corresponding to these mutations led to the identification of a cluster of genes confined to a DNA sequence of about 10 kb required for both biosynthetic and receptor functions.
Mol Microbiol 1991 Jun
PMID:Genetic analysis of the Erwinia chrysanthemi 3937 chrysobactin iron-transport system: characterization of a gene cluster involved in uptake and biosynthetic pathways. 178 88

Transposon mutagenesis and plasmid complementation studies have identified two genes, fepD and fepG, which are essential for ferrienterobactin transport in Escherichia coli. These genes mapped in the enterobactin gene cluster and genetic evidence indicated that they are transcribed as part of an operon (fepD, fepG, fepC). The nucleotide sequence of fepD was determine; it could encode a hydrophobic 33.8 kDa protein with sequence homologies to other iron and vitamin B12 transport proteins. Also identified, between fepD and fepB, was an open reading frame (ORF43) with no detectable function; its 43 kDa protein product (P43) was seen on polyacrylamide gels. The fepD-C operon and ORF43 were divergently transcribed from a 110bp region containing a binding site for the repressor protein Fur.
Mol Microbiol 1991 Jun
PMID:Organization of genes encoding membrane proteins of the Escherichia coli ferrienterobactin permease. 178 94

Oxidant stress has been implicated in reoxygenation damage following hypoxia and can lead to loss of membrane integrity and cell death. In this study the effects of oxidant stress, induced by tert-butyl hydroperoxide (tBHP), on cell conformation and intracellular free calcium ([Ca2+]i) of cardiac myocytes isolated from rat ventricles were examined. Incubation in the presence of 1 mM tBHP lead to a rise in [Ca2+]i, hypercontracture and loss of membrane integrity (as judged by trypan blue staining and loss of fluorescence of fura-2 loaded cells). Incubation in calcium-free medium or medium containing 2,3 butanedione-monoxime (BDM), which decreases myofibrillar calcium sensitivity, delayed but did not prevent the cell shape changes and loss of membrane integrity. In the presence of BDM, hypercontracture occurred at a higher [Ca2+]i than in control cells, indicating a possible role for [Ca2+]i in the generation of hypercontracture in this model. Treatment with calcium antagonists (10(-6) or 10(-7) M nisoldipine or 10(-6) M amlodipine) did not afford any protection against tBHP. ATP depletion did not accelerate loss of membrane integrity. Pretreatment of cells with the iron chelator, desferrioxamine mesylate greatly attenuated the effect of tBPH, delaying the rise in [Ca2+]i, cell shape changes and loss of membrane integrity. It appears, therefore, that tBHP-induced changes are mediated by the iron dependent generation of butyl alkoxyl radicals. The evidence suggests that tBHP-induced contracture is [Ca2+]i dependent rather than ATP dependent. Calcium modifies, but is not essential for the action of tBHP on isolated myocytes. During reoxygenation of hypoxic hearts calcium overload and free radical generation may act synergistically resulting in the characteristic changes associated with this condition, including loss of sarcolemmal integrity.
J Mol Cell Cardiol 1991 Nov
PMID:The role of calcium in the toxic effects of tert-butyl hydroperoxide on adult rat cardiac myocytes. 180 21

In the 40 years of transferrin research, no previous role for apotransferrin has been recognized other than to serve as a plasma carrier for dietary and storage iron. Our studies have revealed a new 'autocrine' growth role for this molecule as well as a possible new cell-cell bridge/CAM function. Certainly, these observations have opened many new areas of investigation both with regard to thyroid hormone action and the function of apotransferrin. In addition, there is now accessible the broader question of tissues other than pituitary which might utilize apotransferrin to regulate responsiveness to thyroid hormones.
Mol Cell Endocrinol 1991 May
PMID:Thyroid hormone regulation of rat pituitary tumor cell growth: a new role for apotransferrin as an autocrine thyromedin. 181 90

The TonB protein plays a key role in the energy-coupled transport of iron siderophores, of vitamin B12, and of colicins of the B-group across the outer membrane of Escherichia coli. In order to obtain more data about which of its particular amino acid sequences are necessary for TonB function, we have cloned and sequenced the tonB gene of Serratia marcescens. The nucleotide sequence predicts an amino acid sequence of 247 residues (Mr 27,389), which is unusually proline-rich and contains the tandem sequences (Glu-Pro)5 and (Lys-Pro)5. In contrast to the TonB proteins of E. coli and Salmonella typhimurium, translation of the S. marcescens TonB protein starts at the first methionine residue of the open reading frame, which is the only amino acid removed during TonB maturation and export. Only the N-terminal sequence is hydrophobic, suggesting its involvement in anchoring the TonB protein to the cytoplasmic membrane. The S. marcescens tonB gene complemented an E. coli tonB mutant with regard to uptake of iron siderophores, and sensitivity to phages T1 and phi 80, and to colicins B and M. However, an E. coli tonB mutant transformed with the S. marcescens tonB gene remained resistant to colicins Ia and Ib, to colicin B derivatives carrying the amino acid replacements Val/Ala and Val/Gly at position 20 in the TonB box, and they exhibited a tenfold lower activity with colicin D. In addition, the S. marcescens TonB protein did not restore T1 sensitivity of an E. coli exbB tolQ double mutant, as has been found for the overexpressed E. coli TonB protein, indicating a lower activity of the S. marcescens TonB protein. Although the S. marcescens TonB protein was less prone to proteolytic degradation, it was stabilized in E. coli by the ExbBD proteins. In E. coli, TonB activity of S. marcescens depended either on the ExbBD or the TolQR activities.
Mol Microbiol 1991 Nov
PMID:The tonB gene of Serratia marcescens: sequence, activity and partial complementation of Escherichia coli tonB mutants. 183 28

The nucleotide sequence of the Escherichia coli fep genomic region has been determined. Three new loci were identified. One of these, P43, encodes a membrane protein that is not essential for ferric enterobactin transport. Two others, fepD and fepG, were found to be essential for transport and their translational products showed extensive homology to other integral membrane proteins involved in TonB-dependent transport processes. The FepC amino acid sequence suggested a peripheral membrane location and revealed conserved ATP-binding domains. Together these data indicate that ferric enterobactin is transported through a typical periplasmic binding protein-dependent system. In addition, the transcriptional organization of these genes was examined and primer extension analysis identified a single iron-regulated bidirectional promoter between the P43 gene and the fepDGC operon.
Mol Microbiol 1991 Jun
PMID:Nucleotide sequence and genetic organization of the ferric enterobactin transport system: homology to other periplasmic binding protein-dependent systems in Escherichia coli. 183 74

Escherichia coli induces the synthesis of at least 30 proteins at the onset of carbon starvation, two-thirds of which are positively regulated by the cyclic AMP (cAMP) and cAMP receptor protein (CRP) complex. Two of the cAMP-CRP-dependent genes mapped to 14 and 93 minutes of the chromosome and are designated cstA and cstB, respectively. The cstA promoter region was cloned and localized to a 600 base-pair fragment downstream from the iron-regulated entCEBA-P15 operon. Carbon starvation-inducible transcription initiated at three sites spaced one turn of the DNA helix apart. All had--10 sequences similar to consensus E sigma 70 promoters and poor--35 sequences. Deletion of a putative CRP binding site abolished carbon starvation-mediated induction. Sequence analysis of the cstA coding region revealed the presence of three sequential open reading frames potentially encoding two hydrophobic proteins of 60,223 Da and 15,201 Da and a hydrophilic protein of 7467 Da. Overexpression of the cstA region produced starvation-inducible proteins of the expected sizes. Suggestive evidence was obtained that cstA is involved in peptide utilization.
J Mol Biol 1991 Mar 05
PMID:Molecular and functional characterization of a carbon starvation gene of Escherichia coli. 184


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