|
|
|
|
|
|
Activities of Two Novel Macrolides, GW 773546 and GW 708408, Compared with Those of Telithromycin, Erythromycin, Azithromycin, and Clarithromycin against Haemophilus influenzae. Klaudia Kosowska, 2004. Expression of a Temperature-Sensitive Esterase in a Novel Chaperone-Based Escherichia coli Strain. Manuel Ferrer, 2004. Activity of Sinorhizobium meliloti NodAB and NodH Enzymes on Thiochitooligosaccharides. Audrey M. Southwick, 2002.Rhizobium bacteria synthesize signal molecules called Nod factors that elicit responses in the legume root during nodulation . Nod factors, modified N-acylated ß-(1,4)-N-acetylglucosamine, are synthesized by the nodulation (nod) gene products . We tested the ability of three Sinorhizobium meliloti nod gene products to modify Nod factor analogs with thio linkages instead of O-glycosidic bonds in the oligosaccharide backbone . Analysis of a DtxR-Like Metalloregulatory Protein, MntR, from Corynebacterium diphtheriae That Controls Expression of an ABC Metal Transporter by an Mn2+-Dependent Mechanism. Michael P. Schmitt, 2002.The DtxR protein is a global iron-dependent repressor in Corynebacterium diphtheriae that regulates transcription from multiple promoters . A search of the partially completed C . diphtheriae genome identified a gene, mntR, whose predicted product has significant homology with the DtxR repressor protein . The mntR gene is the terminal gene in a five-gene operon that also carries the mntABCD genes, whose predicted products are homologous to ABC metal transporters . Transcription of this genetic system, as measured by expression of an mntA-lacZ reporter fusion, is strongly repressed by Mn2+ . The divalent metals Fe2+, Cu2+, and Zn2+ did not repress expression of the mntA-lacZ construct . A mutation in the mntR gene abolished Mn2+-dependent repression of the mntA-lacZ fusion, demonstrating that MntR is essential for the Mn2+-dependent regulation of this promoter . Footprinting experiments showed that MntR protects from DNase I digestion an approximately 73-bp AT-rich region that includes the entire mntA promoter . This large region protected from DNase I suggests that as many as three MntR dimer pairs may bind to this region . Binding studies also revealed that DtxR failed to bind to the MntR binding site and that MntR exhibited weak and diffuse binding at the DtxR binding site at the tox promoter . A C . diphtheriae mntA mutant grew as well as the wild type in a low-Mn2+ medium, which suggests that the mntABCD metal transporter is not required for growth in a low-Mn2+ medium and that additional Mn2+ transport systems may be present in C . diphtheriae . This study reports the characterization of MntR, a Mn2+-dependent repressor, and the second member of the family of DtxR-like metalloregulatory proteins to be identified in C . diphtheriae . Gene Expression Analysis of Energy Metabolism Mutants of Desulfovibrio vulgaris Hildenborough Indicates an Important Role for Alcohol Dehydrogenase. Shelley A. Haveman, 2003.Comparison of the proteomes of the wild-type and Fe-only hydrogenase mutant strains of Desulfovibrio vulgaris Hildenborough, grown in lactate-sulfate (LS) medium, indicated the near absence of open reading frame 2977 (ORF2977)-coded alcohol dehydrogenase in the hyd mutant . Hybridization of labeled cDNA to a macroarray of 145 PCR-amplified D . vulgaris genes encoding proteins active in energy metabolism indicated that the adh gene was among the most highly expressed in wild-type cells grown in LS medium . Relative to the wild type, expression of the adh gene was strongly downregulated in the hyd mutant, in agreement with the proteomic data . Expression was upregulated in ethanol-grown wild-type cells . An adh mutant was constructed and found to be incapable of growth in media in which ethanol was both the carbon source and electron donor for sulfate reduction or was only the carbon source, with hydrogen serving as electron donor . The hyd mutant also grew poorly on ethanol, in agreement with its low level of adh gene expression . The adh mutant grew to a lower final cell density on LS medium than the wild type . These results, as well as the high level of expression of adh in wild-type cells on media in which lactate, pyruvate, formate, or hydrogen served as the sole electron donor for sulfate reduction, indicate that ORF2977 Adh contributes to the energy metabolism of D . vulgaris under a wide variety of metabolic conditions . A hydrogen cycling mechanism is proposed in which protons and electrons originating from cytoplasmic ethanol oxidation by ORF2977 Adh are converted to hydrogen or hydrogen equivalents, possibly by a putative H2-heterodisulfide oxidoreductase complex, which is then oxidized by periplasmic Fe-only hydrogenase to generate a proton gradient .
|
© 2005
Transgalactic Ltd (manufacturer of Bioscreen C software) |
Privacy Statement | P.O. Box
1393, 00101 Helsinki, Finland,
Last modified: May 25, 2005
| ||||||
