scholarly journals Mutant Strains of Escherichia coli K12 That Use D-Amino Acids

1971 ◽  
Vol 68 (10) ◽  
pp. 2484-2487 ◽  
Author(s):  
J. Kuhn ◽  
R. L. Somerville
Keyword(s):  
Escherichia Coli ◽  
Amino Acids ◽  
Escherichia Coli K12 ◽  
Mutant Strains

scholarly journals Enzymic synthesis of N-acetyl-l-phenylalanine in Escherichia coli K12

1971 ◽  
Vol 124 (5) ◽  
pp. 905-913 ◽  
Author(s):  
R. V. Krishna ◽  
P. R. Krishnaswamy ◽  
D. Rajagopal Rao
Keyword(s):  
Escherichia Coli ◽  
Amino Acids ◽  
Amino Acid ◽  
Substrate Specificity ◽  
Acetyl Coa ◽  
Ph Optimum ◽  
E Coli ◽  
Enzymic Synthesis ◽  
Escherichia Coli K12

1. Cell-free extracts of Escherichia coli K12 catalyse the synthesis of N-acetyl-l-phenylalanine from acetyl-CoA and l-phenylalanine. 2. The acetyl-CoA–l-phenylalanine α-N-acetyltransferase was purified 160-fold from cell-free extracts. 3. The enzyme has a pH optimum of 8 and catalyses the acetylation of l-phenylalanine. Other l-amino acids such as histidine and alanine are acetylated at slower rates. 4. A transacylase was also purified from E. coli extracts and its substrate specificity studied. 5. The properties of both these enzymes were compared with those of other known amino acid acetyltransferases and transacylases.

scholarly journals Reconstitution of oxidative phosphorylation and the adenosine triphosphate-dependent transhydrogenase activity by a combination of membrane fractions from uncA− and uncB− mutant strains of Escherichia coli K12

1973 ◽  
Vol 134 (4) ◽  
pp. 1015-1021 ◽  
Author(s):  
G. B. Cox ◽  
F. Gibson ◽  
L. McCann
Keyword(s):  
Escherichia Coli ◽  
Electron Transport ◽  
Oxidative Phosphorylation ◽  
Membrane System ◽  
Normal Strain ◽  
Escherichia Coli K12 ◽  
Functional Relationships ◽  
Transport Chain ◽  
Mutant Strains ◽  
Low Ionic Strength

1. Membrane preparations from both uncA− and uncB− mutant strains of Escherichia coli K12, in which electron transport is uncoupled from phosphorylation, were fractionated by washing with a low-ionic-strength buffer. The fractionation gave a `5mm-Tris wash' and a `membrane residue' from each strain. This technique, applied to membranes from normal cells, separates the Mg2+,Ca2+-stimulated adenosine triphosphatase activity from the membrane-bound electron-transport chain and the non-energy-linked transhydrogenase activity. 2. Reconstitution of both oxidative phosphorylation and the ATP-dependent transhydrogenase activity was obtained by a combination of the `membrane residue' from strain AN249 (uncA−) with the `5mm-Tris wash' from strain AN283 (uncB−). 3. Valinomycin plus NH4+ inhibited oxidative phosphorylation both in membranes from a normal strain of E. coli and in the reconstituted membrane system derived from the mutant strains. 4. The electron-transport-dependent transhydrogenase activity was located in the membrane residue and was de-repressed in both the mutant strains. 5. The spatial and functional relationships between the proteins specified by the uncA and uncB genes and the transhydrogenase protein are discussed.

scholarly journals Synthesis, Antitumor and Antibacterial Studies of New Shortened Analogues of (KLAKLAK)2-NH2 and Their Conjugates Containing Unnatural Amino Acids

Molecules ◽  
2021 ◽  
Vol 26 (4) ◽  
pp. 898
Author(s):  
Sirine Jaber ◽  
Ivan Iliev ◽  
Tsvetelina Angelova ◽  
Veronica Nemska ◽  
Inna Sulikovska ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Amino Acids ◽  
Unnatural Amino Acids ◽  
Antibacterial Properties ◽  
Unnatural Amino Acid ◽  
Moderate Activity ◽  
Escherichia Coli K12 ◽  
Anticancer Properties ◽  
The One ◽  
Natural Amino Acids

(1) Background: (KLAKLAK)2 is a representative of the antimicrobial peptide group which also shows good anticancer properties. (2) Methods: Herein, we report synthesis using SPPS and characterization by HPLC/MS of a series of shortened analogues of (KLAKLAK)2. They contain single sequence KLAKLAK as C-terminal amides. In addition, substitution of some natural amino acids with unnatural β-Ala and nor-Leu is realized. In addition, these structures are conjugated with second pharmacophore with well proven anticancer properties 1,8-naphthalimide or caffeic acid. Cytotoxicity, antiproliferative effect and antimicrobial activity of newly synthesized structures were studied. (3) Results: The obtained experimental results reveal significant selective index for substances with common chemical structure KLβAKLβAK-NH2. The antibacterial properties of newly synthesized analogues at two different concentrations 10 μM and 20 μM, were tested against Gram-negative microorganisms Escherichia coli K12 407. Only two of the studied compounds KLAKLAK-NH2 and the one conjugated with second pharmacophore 1,8-naphthalimide and unnatural amino acid nor-Leu showed moderate activity against tested strains at concentration of 20 μM. (4) Conclusions: The obtained results reveal that the introducing of 1,8-naphthalimideGly- and Caf- increase the cytotoxicity and antiproliferative activity of the peptides but not their selectivity. Only two compounds KLAKLAK-NH2 and 1,8-naphthalimideGKnLAKnLAK-NH2 show moderate activity against Escherichia coli K12 at low concentration of 20 μM.

Nucleotide sequence of the hemG gene involved in the protoporphyrinogen oxidase activity of Escherichia coli K12

1993 ◽  
Vol 39 (12) ◽  
pp. 1155-1161 ◽  
Author(s):  
Alexandre Sasarman ◽  
Jaroslav Letowski ◽  
Guy Czaika ◽  
Volta Ramirez ◽  
Michael A. Nead ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Amino Acids ◽  
Oxidase Activity ◽  
Chlorophyll Biosynthesis ◽  
Protoporphyrin Ix ◽  
Translation System ◽  
Protoporphyrinogen Oxidase ◽  
Escherichia Coli K12 ◽  
Amino Terminal

The hemG gene of Escherichia coli K12 is involved in the activity of protoporphyrinogen oxidase, the enzyme responsible for the conversion of protoporphyrinogen IX into protoporphyrin IX during heme and chlorophyll biosynthesis. The gene is located at min 87 on the genetic map of E. coli K12. The hemG gene was isolated by a mini-Mu in vivo cloning procedure. As expected, the hemG gene is able to restore normal growth to the hemG mutant, and the transformed cells display strong protoporphyrinogen oxidase activity. Sequencing of the hemG gene allowed us to identify an open reading frame of 546 nucleotides (181 amino acids), within the minimal fragment able to complement the mutant. The presumed molecular mass of the HemG protein is 21 202 Da, in agreement with values found by SDS-PAGE, in a DNA-directed coupled transcription–translation system. The identity of the first 18 amino acids at the amino-terminal end of the protein was confirmed by microsequencing. To our knowledge, this is the first cloning of a gene involved in the protoporphyrinogen oxidase activity of E. coli.Key words: protoporphyrinogen oxidase (PROTOX), hemG gene, Escherichia coli, DPE herbicides, heme.

The Roles of Klenow Processing and Flap Processing Activities of DNA Polymerase I in Chromosome Instability in Escherichia coli K12 Strains

Genetics ◽  
2002 ◽  
Vol 160 (1) ◽  
pp. 13-23
Author(s):  
Yuki Nagata ◽  
Kazumi Mashimo ◽  
Masakado Kawata ◽  
Kazuo Yamamoto
Keyword(s):  
Escherichia Coli ◽  
Dna Polymerase ◽  
Chromosome Instability ◽  
Spontaneous Mutations ◽  
Dna Polymerase I ◽  
Escherichia Coli K12 ◽  
Mutant Strains ◽  
Exonuclease Domain ◽  
Polymerase I

Abstract The sequences of spontaneous mutations occurring in the endogenous tonB gene of Escherichia coli in the ΔpolA and polA107 mutant strains were compared. Five categories of mutations were found: (1) deletions, (2) minus frameshifts, (3) plus frameshifts, (4) duplications, and (5) other mutations. The ΔpolA strain, which is deficient in both Klenow domain and 5′ → 3′ exonuclease domain of DNA polymerase I, shows a marked increase in categories 1–4. The polA107 strain, which is deficient in the 5′ → 3′ exonuclease domain but proficient in the Klenow domain, shows marked increases in categories 3 and 4 but not in 1 or 2. Previously, we reported that the polA1 strain, which is known to be deficient in the Klenow domain but proficient in the 5′ → 3′ exonuclease domain, shows increases in categories 1 and 2 but not in 3 or 4. The 5′ → 3′ exonuclease domain of DNA polymerase I is a homolog of the mammalian FEN1 and the yeast RAD27 flap nucleases. We therefore proposed the model that the Klenow domain can process deletion and minus frameshift mismatch in the nascent DNA and that flap nuclease can process plus frameshift and duplication mismatch in the nascent DNA.

scholarly journals Metabolite transport in mutants of Escherichia coli K12 defective in electron transport and coupled phosphorylation

1975 ◽  
Vol 146 (2) ◽  
pp. 417-423 ◽  
Author(s):  
H Rosenberg ◽  
G B Cox ◽  
J D Butlin ◽  
S J Gutowski
Keyword(s):  
Escherichia Coli ◽  
Electron Transport ◽  
Active Transport ◽  
Adenosine Triphosphatase ◽  
Minimal Medium ◽  
Sole Source ◽  
Whole Cells ◽  
Escherichia Coli K12 ◽  
Mutant Strains ◽  
Uptake Medium

1. The uptakes of Pi and serine by whole cells of mutant strains of Escherichia coli K12, grown under both aerobic and anaerobic conditions, were studied. 2. Uptake by aerobic cells was low in a ubiquinone-less mutant but normal in two mutant strains unable to couple phosphorylation to electron transport. 3. One of these uncoupled strains, carrying the unc-405 allele, does not form a membrane-bound Mg2+-stimulated adenosine triphosphatase aggregate, and it is concluded that the Mg2+-stimulated adenosine triphosphatase does not serve a structural role in the aerobic active transport of Pi or serine. 4. The other uncoupled strain, in which aerobic uptake is unaffected, carries a mutation in the uncB gene, thus distinguishing this gene from the etc gene, previously shown to be concerned with the coupling of electron transport to active transport. 5. The uptakes of Pi and serine by anaerobic cells were normal in the ubiquinone-less mutant, but defective in both the uncoupled strains. 6. The uptake of Pi and serine by anaerobic cells of the uncB mutant could be increased by the addition of fumarate to the uptake medium. The unc-405 mutant, however, required the addition of fumarate for growth and for uptake. 7. The uncB mutant, unlike the unc-405 mutant, is able to grow anaerobically in a minimal medium with glucose as sole source of carbon. Similarly a strain carrying a mutation in the frd gene, which is the structural gene for the enzyme fumarate reductase, is able to grow anaerobically in a glucose-minimal medium. However, a mutant strain carrying mutations in both the uncB and frd genes resembles the unc-405 mutant in not being able to grow under these conditions.

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