Synthesis of β-glucans by Bradyrhizobium japonicum and Rhizobium fredii

1992 ◽  
Vol 38 (6) ◽  
pp. 510-514 ◽  
Author(s):  
Arvind A. Bhagwat ◽  
Donald L. Keister
Keyword(s):  
Molecular Weight ◽  
Nitrogen Fixation ◽  
Membrane Protein ◽  
Bradyrhizobium Japonicum ◽  
Rhizobium Meliloti ◽  
Uridine Diphosphate ◽  
Enzyme Preparations ◽  
Rhizobium Fredii ◽  
Diphosphate Glucose

Particulate enzyme preparations from Rhizobium and Bradyrhizobium synthesize β-glucans when incubated with uridine diphosphate glucose (UDP-glucose) and a divalent cation. Synthesis of β-1,2-linked glucans in Rhizobium fredii involves the product of the ndvB gene, a 319-kDa membrane protein, which is labeled with [14C]glucose from UDP-[14C]glucose as previously demonstrated in Rhizobium meliloti and Agrobacterium sp. Bradyrhizobium japonicum synthesize β-1,3- and β-1,6-linked glucans of a lower molecular weight than those synthesized by R. meliloti. In comparative experiments, no evidence was found for a protein-bound intermediate in B. japonicum. The ndvB gene of R. fredii was mobilized to B. japonicum and the gene was expressed, as evidenced by appearance of a large membrane protein (ca. 319 kDa) which was labeled with UDP-[14C]glucose in vitro. Key words: soybean, nitrogen fixation, β-glucan, Bradyrhizobium, Rhizobium.

Uridine diphosphate glucose synthase from calf liver. Determinants of enzyme activity in vitro

Biochemistry ◽  
1975 ◽  
Vol 14 (25) ◽  
pp. 5445-5450 ◽  
Author(s):  
Peter J. Roach ◽  
Kenneth R. Warren ◽  
Daniel E. Atkinson
Keyword(s):  
Enzyme Activity ◽  
Uridine Diphosphate ◽  
Uridine Diphosphate Glucose ◽  
Diphosphate Glucose

scholarly journals New Target Genes Controlled by the Bradyrhizobium japonicum Two-Component Regulatory System RegSR

2007 ◽  
Vol 189 (24) ◽  
pp. 8928-8943 ◽  
Author(s):  
Andrea Lindemann ◽  
Annina Moser ◽  
Gabriella Pessi ◽  
Felix Hauser ◽  
Markus Friberg ◽  
...  
Keyword(s):  
Gene Expression ◽  
Nitrogen Fixation ◽  
Bradyrhizobium Japonicum ◽  
Target Genes ◽  
Regulatory Gene ◽  
Wild Type ◽  
Transcription Profiling ◽  
Two Component ◽  
Regulated Gene Expression

ABSTRACT RegSR-like proteins, members of the family of two-component regulatory systems, are present in a large number of proteobacteria in which they globally control gene expression mostly in a redox-responsive manner. The controlled target genes feature an enormous functional diversity. In Bradyrhizobium japonicum, the facultative root nodule symbiont of soybean, RegSR activate the transcription of the nitrogen fixation regulatory gene nifA, thus forming a RegSR-NifA cascade which is part of a complex regulatory network for gene regulation in response to changing oxygen concentrations. Whole-genome transcription profiling was performed here in order to assess the full regulatory scope of RegSR. The comparative analysis of wild-type and ΔregR cells grown under oxic and microoxic conditions revealed that expression of almost 250 genes is dependent on RegR, a result that underscores the important contribution of RegR to oxygen- or redox-regulated gene expression in B. japonicum. Furthermore, transcription profiling of ΔregR bacteroids compared with wild-type bacteroids revealed expression changes for about 1,200 genes in young and mature bacteroids. Incidentally, many of these were found to be induced in symbiosis when wild-type bacteroids were compared with free-living, culture-grown wild-type cells, and they appeared to encode diverse functions possibly related to symbiosis and nitrogen fixation. We demonstrated direct RegR-mediated control at promoter regions of several selected target genes by means of DNA binding experiments and in vitro transcription assays, which revealed six novel direct RegR target promoters.

Similarities between legume–rhizobium communication and steroid-mediated intercellular communication in vertebrates

1992 ◽  
Vol 38 (6) ◽  
pp. 541-547 ◽  
Author(s):  
Michael E. Baker
Keyword(s):  
Nitrogen Fixation ◽  
Biological Activity ◽  
Amino Acid ◽  
Bradyrhizobium Japonicum ◽  
Common Ancestor ◽  
Rhizobium Meliloti ◽  
Hydroxysteroid Dehydrogenase ◽  
Nod Factors ◽  
Sequence Analyses ◽  
Metabolizing Enzymes

Regulation of the actions of flavonoids and Nod factors in legume–rhizobia communication has several interesting similarities with that of steroid-mediated actions in vertebrates. Oxidation or reduction of flavonoids and Nod factors modifies their biological activity just as, for example, oxidation of an alcohol at C11 on hydrocortisone regulates its biological activity. Second, some flavonoids are anti-inducers, functioning like steroid antagonists to negate the actions of inducer flavonoids. Amino acid sequence analyses show that human 17β-hydroxysteroid dehydrogenase, which catalyzes the interconversion of the alcohol and ketone at C17 on estrogens and androgens, and rat 11β-hydroxysteroid dehydrogenase, which catalyzes the interconversion of the alcohol and ketone at C11 of glucocorticoids, and Rhizobium meliloti NodG and Bradyrhizobium japonicum. FixR are derived from a common ancestor. Just as steroid-metabolizing enzymes can regulate steroid-mediated gene transcription, enzymes that modify substituents on flavonoids and Nod factors may have a similar role in regulating signalling between legumes and rhizobia. The enzymes that modify flavonoids and Nod factors have not yet been identified. However, NodG and FixR are two likely candidates to have this role in regulating legume–rhizobia signalling. Key words: NodG function, FixR function, steroid–flavonoid similarities, steroids and nitrogen fixation.

scholarly journals Endogenous glycosyltransferases glucosylate lipids in flagella of Euglena.

1984 ◽  
Vol 98 (5) ◽  
pp. 1825-1835 ◽  
Author(s):  
S J Chen ◽  
G B Bouck
Keyword(s):  
Molecular Weight ◽  
Soluble Fraction ◽  
Uridine Diphosphate ◽  
Cell Surfaces ◽  
Combined Use ◽  
Layer Chromatography ◽  
Chloroform Methanol ◽  
Isolated Cell

Flagella, intact deflagellated cells and isolated cell surfaces of the unicell , Euglena were separately assayed for glycosyltransferase activity by incubating these fractions with uridine diphosphate-[3H]glucose and isolating radiolabeled products. Most of the label was incorporated into lipophilic products, soluble in chloroform/methanol, which could be separated via thin layer chromatography or LH-60 chromatography into four distinct classes. The most polar of these products was extracted from flagella and purified by column chromatography for use as an in vitro substrate to identify flagella-associated glycosyltransferases. After flagella were treated with the detergent CHAPS , a soluble fraction was removed that was capable of glycosylation in solution. The glycosyltransferase(s) responsible for this activity were further enriched on sucrose or fructose gradients and ultimately identified on acrylamide gels through the combined use of nondenaturing gels, dial-[3H]uridine diphosphate binding, and fluorography. The enzyme had an apparent monomer molecular weight of 32,000 and consisted of four or fewer subunits. The occurrence of endogenous glycosyltransferase(s) in flagella suggests that modifications and/or assembly of the flagella surface can take place in situ in this organism.

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