scholarly journals 1-(o-Carboxyphenylamino)-1-deoxyribulose. A compound formed by mutant strains of Aerobacter aerogenes and Escherichia coli blocked in the biosynthesis of tryptophan

1959 ◽  
Vol 72 (4) ◽  
pp. 586-597 ◽  
Author(s):  
C. H. Doy ◽  
F. Gibson
Keyword(s):  
Escherichia Coli ◽  
Aerobacter Aerogenes ◽  
Mutant Strains

scholarly journals Anthranilate synthase/anthranilate 5-phosphoribosyl 1-pyrophosphate phosphoribosyltransferase from Aerobacter aerogenes

1972 ◽  
Vol 130 (3) ◽  
pp. 847-859 ◽  
Author(s):  
A. F. Egan ◽  
F. Gibson
Keyword(s):  
Escherichia Coli ◽  
Kinetic Studies ◽  
Competitive Inhibitor ◽  
Active Enzyme ◽  
The Other ◽  
Anthranilate Synthase ◽  
Aerobacter Aerogenes ◽  
Auxotrophic Mutants ◽  
Mutant Strains ◽  
Sequential Mechanism

1. Anthranilate synthase and phosphoribosyltransferase from Aerobacter aerogenes purify simultaneously and sediment together on sucrose gradients, showing that they occur as an enzyme aggregate. Both activities of the intact aggregate are subject to inhibition by tryptophan. 2. By using appropriate auxotrophic mutants it was shown that an intact active enzyme aggregate is formed when the components come from separate mutant strains. An intact active aggregate can also be formed when one component is from Escherichia coli and the other from A. aerogenes. 3. Phosphoribosyltransferase of A. aerogenes is active when not in an aggregate with anthranilate synthase, but is not subject to tryptophan inhibition, indicating that the inhibitor site is on the anthranilate synthase component. 4. Anthranilate synthase can be active and sensitive to tryptophan inhibition when complexed with an inactive phosphoribosyltransferase. 5. Kinetic studies on the anthranilate synthase activity show that tryptophan is a competitive inhibitor with respect to chorismate and a non-competitive inhibitor with respect to either glutamine or NH4+ ions. This is consistent with a sequential mechanism of the ordered type in which chorismate is the first reactant.

scholarly journals Identification of the l,d-Transpeptidases Responsible for Attachment of the Braun Lipoprotein to Escherichia coli Peptidoglycan

2007 ◽  
Vol 189 (10) ◽  
pp. 3927-3931 ◽  
Author(s):  
Sophie Magnet ◽  
Samuel Bellais ◽  
Lionel Dubost ◽  
Martine Fourgeaud ◽  
Jean-Luc Mainardi ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Enterococcus Faecium ◽  
Resistant Mutant ◽  
Cross Linking ◽  
Mutant Strains ◽  
Acyl Acceptors

ABSTRACT The l,d-transpeptidase Ldtfm catalyzes peptidoglycan cross-linking in β-lactam-resistant mutant strains of Enterococcus faecium. Here, we show that in Escherichia coli Ldtfm homologues are responsible for the attachment of the Braun lipoprotein to murein, indicating that evolutionarily related domains have been tailored to use muropeptides or proteins as acyl acceptors in the l,d-transpeptidation reaction.

Sensitivity of normal and mutant strains of Escherichia coli to actinomycin-D

1972 ◽  
Vol 18 (6) ◽  
pp. 909-915 ◽  
Author(s):  
A. P. Singh ◽  
K.-J. Cheng ◽  
J. W. Costerton ◽  
E. S. Idziak ◽  
J. M. Ingram
Keyword(s):  
Escherichia Coli ◽  
Cell Wall ◽  
Wild Type Strain ◽  
Actinomycin D ◽  
Cytoplasmic Membrane ◽  
Cell Envelope ◽  
Coli Strain ◽  
Wild Type ◽  
Mutant Strains ◽  
In The Wild

The site of the cell barrier to actinomycin-D uptake was studied using a wild-type Escherichia coli strain P and its cell envelope-defective filamentous mutants, strains 6γ and 12γ, both of which 'leak' β-galactosidase and alkaline phosphatase into the medium during growth indicating both membrane and cell-wall defects. Actinomycin-D entered the cells of these two mutant strains as evidenced by the inhibition of both 14C-uracil incorporation and synthesis of the induced β-galactosidase system. Under similar conditions, no inhibition occurred in the wild-type strain and its sucrose-lysozyme prepared spheroplasts. Actinomycin-D did, however, inhibit the above-mentioned systems in the wild-type sucrose-lysozyme spheroplasts prepared in the presence of 2 mM EDTA. The experimental data indicate that although the cell wall may act as a primary barrier or sieve to actinomycin-D, the cytoplasmic membrane should be considered the final and determinative barrier to this antibiotic.

scholarly journals Overproduction of Inactive Variants of the Murein Synthase PBP1B Causes Lysis in Escherichia coli

2003 ◽  
Vol 185 (18) ◽  
pp. 5342-5348 ◽  
Author(s):  
Ute Meisel ◽  
Joachim-Volker Höltje ◽  
Waldemar Vollmer
Keyword(s):  
Escherichia Coli ◽  
Single Amino Acid ◽  
Penicillin Binding Protein ◽  
Amino Acid Exchange ◽  
Lytic Transglycosylases ◽  
Mutant Strains ◽  
Ph Conditions ◽  
Expression Plasmids ◽  
Acid Exchange

ABSTRACT Penicillin-binding protein 1B (PBP1B) of Escherichia coli is a bifunctional murein synthase containing both a transpeptidase domain and a transglycosylase domain. The protein is present in three forms (α, β, and γ) which differ in the length of their N-terminal cytoplasmic region. Expression plasmids allowing the production of native PBP1B or of PBP1B variants with an inactive transpeptidase or transglycosylase domain or both were constructed. The inactive domains contained a single amino acid exchange in an essential active-site residue. Overproduction of the inactive PBP1B variants, but not of the active proteins, caused lysis of wild-type cells. The cells became tolerant to lysis by inactive PBP1B at a pH of 5.0, which is similar to the known tolerance for penicillin-induced lysis under acid pH conditions. Lysis was also reduced in mutant strains lacking several murein hydrolases. In particular, a strain devoid of activity of all known lytic transglycosylases was virtually tolerant, indicating that mainly the lytic transglycosylases are responsible for the observed lysis effect. A possible structural interaction between PBP1B and murein hydrolases in vivo by the formation of a multienzyme complex is discussed.

scholarly journals CpxP, a Stress-Combative Member of the Cpx Regulon

1998 ◽  
Vol 180 (4) ◽  
pp. 831-839 ◽  
Author(s):  
Paul N. Danese ◽  
Thomas J. Silhavy
Keyword(s):  
Escherichia Coli ◽  
Envelope Protein ◽  
Periplasmic Protein ◽  
Dependent Manner ◽  
Alkaline Ph ◽  
Signal Transduction System ◽  
Two Component ◽  
Mutant Strains ◽  
Alkaline Conditions ◽  
Two Component Signal Transduction

ABSTRACT The CpxA/R two-component signal transduction system ofEscherichia coli can combat a variety of extracytoplasmic protein-mediated toxicities. The Cpx system performs this function, in part, by increasing the synthesis of the periplasmic protease, DegP. However, other factors are also employed by the Cpx system for this stress-combative function. In an effort to identify these remaining factors, we screened a collection of random lacZ operon fusions for those fusions whose transcription is regulated by CpxA/R. Through this approach, we have identified a new locus,cpxP, whose transcription is stimulated by activation of the Cpx pathway. cpxP specifies a periplasmic protein that can combat the lethal phenotype associated with the synthesis of a toxic envelope protein. In addition, we show that cpxPtranscription is strongly induced by alkaline pH in a CpxA-dependent manner and that cpxP and cpx mutant strains display hypersensitivity to growth in alkaline conditions.

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