scholarly journals Recognition of 2′-hydroxyl groups by Escherichia coli ribonuclease HI

FEBS Letters ◽  
1995 ◽  
Vol 368 (2) ◽  
pp. 315-320 ◽  
Author(s):  
Shigenori Iwai ◽  
Shin Kataoka ◽  
Makoto Wakasa ◽  
Eiko Ohtsuka ◽  
Haruki Nakamura
Keyword(s):  
Escherichia Coli ◽  
Hydroxyl Groups

scholarly journals Citrate Sensing by the C4-Dicarboxylate/Citrate Sensor Kinase DcuS of Escherichia coli: Binding Site and Conversion of DcuS to a C4-Dicarboxylate- or Citrate-Specific Sensor

2007 ◽  
Vol 189 (11) ◽  
pp. 4290-4298 ◽  
Author(s):  
J. Krämer ◽  
J. D. Fischer ◽  
E. Zientz ◽  
V. Vijayan ◽  
C. Griesinger ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Protein Kinase ◽  
Binding Site ◽  
Hydroxyl Groups ◽  
Sensor Kinase ◽  
Histidine Protein Kinase ◽  
Carboxylic Groups ◽  
Periplasmic Domain

ABSTRACT The histidine protein kinase DcuS of Escherichia coli senses C4-dicarboxylates and citrate by a periplasmic domain. The closely related sensor kinase CitA binds citrate, but no C4-dicarboxylates, by a homologous periplasmic domain. CitA is known to bind the three carboxylate and the hydroxyl groups of citrate by sites C1, C2, C3, and H. DcuS requires the same sites for C4-dicarboxylate sensing, but only C2 and C3 are highly conserved. It is shown here that sensing of citrate by DcuS required the same sites. Binding of citrate to DcuS, therefore, was similar to binding of C4-dicarboxylates but different from that of citrate binding in CitA. DcuS could be converted to a C4-dicarboxylate-specific sensor (DcuSDC) by mutating residues of sites C1 and C3 or of some DcuS-subtype specific residues. Mutations around site C1 aimed at increasing the size and accessibility of the site converted DcuS to a citrate-specific sensor (DcuSCit). DcuSDC and DcuSCit had complementary effector specificities and responded either to C4-dicarboxylates or to citrate and mesaconate. The results imply that DcuS binds citrate (similar to the C4-dicarboxylates) via the C4-dicarboxylate part of the molecule. Sites C2 and C3 are essential for binding of two carboxylic groups of citrate or of C4-dicarboxylates; sites C1 and H are required for other essential purposes.

scholarly journals Substrate Specificity of a Mannose-6-Phosphate Isomerase from Bacillus subtilis and Its Application in the Production of l-Ribose

2009 ◽  
Vol 75 (14) ◽  
pp. 4705-4710 ◽  
Author(s):  
Soo-Jin Yeom ◽  
Jung-Hwan Ji ◽  
Nam-Hee Kim ◽  
Chang-Su Park ◽  
Deok-Kun Oh
Keyword(s):  
Escherichia Coli ◽  
Bacillus Subtilis ◽  
Substrate Specificity ◽  
Maximal Activity ◽  
Pharmaceutical Compounds ◽  
Recombinant Enzyme ◽  
Hydroxyl Groups ◽  
Conversion Yield ◽  
Uncharacterized Gene ◽  
Mannose 6 Phosphate

ABSTRACT The uncharacterized gene previously proposed as a mannose-6-phosphate isomerase from Bacillus subtilis was cloned and expressed in Escherichia coli. The maximal activity of the recombinant enzyme was observed at pH 7.5 and 40°C in the presence of 0.5 mM Co2+. The isomerization activity was specific for aldose substrates possessing hydroxyl groups oriented in the same direction at the C-2 and C-3 positions, such as the d and l forms of ribose, lyxose, talose, mannose, and allose. The enzyme exhibited the highest activity for l-ribulose among all pentoses and hexoses. Thus, l-ribose, as a potential starting material for many l-nucleoside-based pharmaceutical compounds, was produced at 213 g/liter from 300-g/liter l-ribulose by mannose-6-phosphate isomerase at 40°C for 3 h, with a conversion yield of 71% and a volumetric productivity of 71 g liter−1 h−1.

scholarly journals A promiscuous archaeal cardiolipin synthase generating a variety of cardiolipins and phospholipids

2020 ◽  
Author(s):  
Marten Exterkate ◽  
Niels A. W. de Kok ◽  
Ruben L. H. Andringa ◽  
Niels H. J. Wolbert ◽  
Adriaan J. Minnaard ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Lipid Membranes ◽  
Ether Lipid ◽  
Transesterification Reaction ◽  
Hydroxyl Groups ◽  
Glycerol Backbone ◽  
Methanospirillum Hungatei ◽  
Primary Hydroxyl ◽  
Cardiolipin Synthase ◽  
Phospholipid Species

AbstractCardiolipin (DPCL) biosynthesis has barely been explored in Archaeal isoprenoid-based ether lipid membranes. Here, we identified a cardiolipin synthase (MhCls) from the mesophilic anaerobic methanogen Methanospirillum hungatei. The enzyme was overexpressed in Escherichia coli, purified, and subsequently characterized by LC-MS. MhCls utilizes two archaetidylglycerol molecules in a transesterification reaction to synthesize archaeal di-phosphate cardiolipin (aDPCL) and glycerol. The enzyme is invariant to the stereochemistry of the glycerol-backbone and the nature of the lipid tail, as it also accepts phosphatidylglycerol to generate di-phosphate cardiolipin (DPCL). Remarkably, in the presence of archaetidylglycerol and phosphatidylglycerol, MhCls formed an archaeal-bacterial hybrid di-phosphate cardiolipin (hDPCL), that so far has not been observed in nature. Due to the reversibility of the transesterification, cardiolipin can be converted back in presence of glycerol into phosphatidylglycerol. In the presence of other compounds that contain primary hydroxyl groups (e.g. alcohols, water, sugars) various natural and unique artificial phospholipid species could be synthesized, including multiple di-phosphate cardiolipin species. Moreover, MhCls could utilize a glycolipid in the presence of phosphatidylglycerol to form a glycosyl-mono-phosphate cardiolipin, emphasizing the promiscuity of this cardiolipin synthase.

scholarly journals Biotransformation of Natural and Synthetic Isoflavonoids by Two Recombinant Microbial Enzymes

2003 ◽  
Vol 69 (9) ◽  
pp. 5045-5050 ◽  
Author(s):  
Michael Seeger ◽  
Myriam González ◽  
Beatriz Cámara ◽  
Liliana Muñoz ◽  
Emilio Ponce ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Escherichia Coli ◽  
Nuclear Magnetic Resonance ◽  
Gas Chromatography ◽  
Biological Activities ◽  
Gas Chromatography Mass Spectrometry ◽  
Attractive Alternative ◽  
Hydroxyl Groups ◽  
Microbial Enzymes ◽  
Biotransformation Products

ABSTRACT Isolation and synthesis of isoflavonoids has become a frequent endeavor, due to their interesting biological activities. The introduction of hydroxyl groups into isoflavonoids by the use of enzymes represents an attractive alternative to conventional chemical synthesis. In this study, the capabilities of biphenyl-2,3-dioxygenase (BphA) and biphenyl-2,3-dihydrodiol 2,3-dehydrogenase (BphB) of Burkholderia sp. strain LB400 to biotransform 14 isoflavonoids synthesized in the laboratory were investigated by using recombinant Escherichia coli strains containing plasmid vectors expressing the bphA1A2A3A4 or bphA1A2A3A4B genes of strain LB400. The use of BphA and BphB allowed us to biotransform 7-hydroxy-8-methylisoflavone and 7-hydroxyisoflavone into 7,2′,3′-trihydroxy-8-methylisoflavone and 7,3′,4′-trihydroxyisoflavone, respectively. The compound 2′-fluoro-7-hydroxy-8-methylisoflavone was dihydroxylated by BphA at ortho-fluorinated and meta positions of ring B, with concomitant dehalogenation leading to 7,2′,3′,-trihydroxy-8-methylisoflavone. Daidzein (7,4′-dihydroxyisoflavone) was biotransformed by BphA, generating 7,2′,4′-trihydroxyisoflavone after dehydration. Biotransformation products were analyzed by gas chromatography-mass spectrometry and nuclear magnetic resonance techniques.

Structural organization of escherichia coli ribosomes as determined by immuno electron microscopy

1978 ◽  
Vol 36 (2) ◽  
pp. 166-167 ◽  
Author(s):  
G. Stöffler ◽  
R.W. Bald ◽  
J. Dieckhoff ◽  
H. Eckhard ◽  
R. Lührmann ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Escherichia Coli ◽  
Ribosomal Proteins ◽  
Structural Organization ◽  
Three Dimensional ◽  
Ribosomal Subunit ◽  
Spatial Arrangement ◽  
Small Subunit ◽  
Antibody Binding ◽  
Immuno Electron Microscopy

A central step towards an understanding of the structure and function of the Escherichia coli ribosome, a large multicomponent assembly, is the elucidation of the spatial arrangement of its 54 proteins and its three rRNA molecules. The structural organization of ribosomal components has been investigated by a number of experimental approaches. Specific antibodies directed against each of the 54 ribosomal proteins of Escherichia coli have been performed to examine antibody-subunit complexes by electron microscopy. The position of the bound antibody, specific for a particular protein, can be determined; it indicates the location of the corresponding protein on the ribosomal surface.The three-dimensional distribution of each of the 21 small subunit proteins on the ribosomal surface has been determined by immuno electron microscopy: the 21 proteins have been found exposed with altogether 43 antibody binding sites. Each one of 12 proteins showed antibody binding at remote positions on the subunit surface, indicating highly extended conformations of the proteins concerned within the 30S ribosomal subunit; the remaining proteins are, however, not necessarily globular in shape (Fig. 1).

Sites of Adsorption of the Bacteriophages T3 and T5 on the Wall of Escherichia Coli B.

1967 ◽  
Vol 25 ◽  
pp. 96-97
Author(s):  
Manfred E. Bayer
Keyword(s):  
Escherichia Coli ◽  
Cell Wall ◽  
Electron Microscope ◽  
Uranyl Acetate ◽  
E Coli ◽  
Receptor Sites ◽  
Rigid Cell Wall ◽  
Host Cell Surface ◽  
Bacterial Viruses ◽  
Escherichia Coli B

Bacterial viruses adsorb specifically to receptors on the host cell surface. Although the chemical composition of some of the cell wall receptors for bacteriophages of the T-series has been described and the number of receptor sites has been estimated to be 150 to 300 per E. coli cell, the localization of the sites on the bacterial wall has been unknown.When logarithmically growing cells of E. coli are transferred into a medium containing 20% sucrose, the cells plasmolize: the protoplast shrinks and becomes separated from the somewhat rigid cell wall. When these cells are fixed in 8% Formaldehyde, post-fixed in OsO4/uranyl acetate, embedded in Vestopal W, then cut in an ultramicrotome and observed with the electron microscope, the separation of protoplast and wall becomes clearly visible, (Fig. 1, 2). At a number of locations however, the protoplasmic membrane adheres to the wall even under the considerable pull of the shrinking protoplast. Thus numerous connecting bridges are maintained between protoplast and cell wall. Estimations of the total number of such wall/membrane associations yield a number of about 300 per cell.

Infection of Escherichia coli with bacteriophages

1969 ◽  
Vol 27 ◽  
pp. 370-371
Author(s):  
Manfred E. Bayer
Keyword(s):  
Escherichia Coli ◽  
Nucleic Acid ◽  
Cell Surface ◽  
Virus Type ◽  
Infection Process ◽  
Adsorption Site ◽  
The Other ◽  
Specific Receptors ◽  
Bacterial Receptors

The first step in the infection of a bacterium by a virus consists of a collision between cell and bacteriophage. The presence of virus-specific receptors on the cell surface will trigger a number of events leading eventually to release of the phage nucleic acid. The execution of the various "steps" in the infection process varies from one virus-type to the other, depending on the anatomy of the virus. Small viruses like ØX 174 and MS2 adsorb directly with their capsid to the bacterial receptors, while other phages possess attachment organelles of varying complexity. In bacteriophages T3 (Fig. 1) and T7 the small conical processes of their heads point toward the adsorption site; a welldefined baseplate is attached to the head of P22; heads without baseplates are not infective.

The Nature of the Intramembrane Particle

1980 ◽  
Vol 38 ◽  
pp. 688-691
Author(s):  
A.J. Verkleij
Keyword(s):  
Escherichia Coli ◽  
Tight Junction ◽  
Gap Junction ◽  
The Other ◽  
Fracture Face ◽  
Band 3 Protein ◽  
Satisfactory Explanation ◽  
Freeze Fracturing ◽  
Intramembrane Particle ◽  
Luminal Membrane

Freeze-fracturing splits membranes into two helves, thus allowing an examination of the membrane interior. The 5-10 rm particles visible on both monolayers are widely assumed to be proteinaceous in nature. Most membranes do not reveal impressions complementary to particles on the opposite fracture face, if the membranes are fractured under conditions without etching. Even if it is considered that shadowing, contamination or fracturing itself might obscure complementary pits', there is no satisfactory explanation why under similar physical circimstances matching halves of other membranes can be visualized. A prominent example of uncomplementarity is found in the erythrocyte manbrane. It is wall established that band 3 protein and possibly glycophorin represents these nonccmplanentary particles. On the other hand a number of membrane types show pits opposite the particles. Scme well known examples are the ";gap junction',"; tight junction, the luminal membrane of the bladder epithelial cells and the outer membrane of Escherichia coli.

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