The Escherichia coli metallo-regulator RcnR represses rcnA and rcnR transcription through binding on a shared operator site: Insights into regulatory specificity towards nickel and cobalt

ABSTRACT In Escherichia coli, the exu regulon of the hexuronate system involves the three exuT, uxaCA and uxaB operons and is under the negative control of the exuR regulatory gene product. The technique developed by Casadaban, Chou and Cohen was employed to construct two plasmids containing operon fusions in which the lactose genes were fused to the uxaCA and exuT operons. These fusions were transferred into the chromosome by a reciprocal recombination event, and the resulting strains were used for isolation of mutants defective in repression. Two types of operator-constitutive mutants were obtained: one specific for the uxaCA operon expression and the other affecting the exuT gene expression. This genetic evidence confirms that these two operons which are divergently transcribed each possess their own operator site.—The derepressed expression of the two exuT-lac and uxaCA-lac operons and the uxaB gene was also examined upon introduction of plasmids bearing various operators of the exu regulon. The results of testing exuR repressor titration by multiple copies of the exu operators allowed us to show a gradation in the affinity degrees for the three exu operators: uxaBo has the strongest affinity for the exuR repressor and uxaCo the weakest, although that of exuTo seems to be just slightly greater. This gradation may play a role in the control of the exu regulon expression.

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NEW MAP LOCATION OF ilvO IN ESCHERICHIA COLI

Genetics ◽

10.1093/genetics/83.2.201 ◽

1976 ◽

Vol 83 (2) ◽

pp. 201-225

Author(s):

Bruce M Cohen ◽

Elizabeth W Jones

Keyword(s):

Escherichia Coli ◽

Gene Order ◽

Genetic Material ◽

Gene Products ◽

E Coli ◽

K 12 ◽

Map Location ◽

Operator Site

ABSTRACT Mutations in ilvO, the operator site for operon A of the ilv region of E. coli K-12, are reported to cause a cis dominant derepression of the operon A gene products and to map between ilvC and ilvA. Studies reported here demonstrate that the F25 episome which does not carry the region between ilvC and ilvAbut only ilvE, ilvD and a part of ilvA, can transfer ilvO genetic material. Also, genes of operon A on the F25 episome respond normally to a derepression signal. It is proposed that ilvO is on the F25 episome. Five-point crosses demonstrate that mutations in ilvOmap nearer to ilvE than to ilvA. Considering this and other evidence, it is proposed that the gene order in the ilv region is CADEO, not COADE, with transcription and translation in operon A being from ilvE to ilvA not ilvA to ilvE. It is confirmed that mutations in ilvO cause a cis dominant derepression of the operon A gene products but it is also noted that mutations in ilvO lead to the appearance of an AHAS activity more resistant to inhibition by valine than that of the present O+ strain.

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

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100081693 ◽

1978 ◽

Vol 36 (2) ◽

pp. 166-167 ◽

Cited By ~ 1

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).

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

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100060490 ◽

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.

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Infection of Escherichia coli with bacteriophages

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100063767 ◽

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.

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The Nature of the Intramembrane Particle

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s1431927600003020 ◽

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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