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The Lactobacillus casei ptsHI47T Mutation Causes Overexpression of a LevR-Regulated but RpoN-Independent Operon Encoding a Mannose Class Phosphotransferase System. Alain Mazé, 2004.A proteome analysis of Lactobacillus casei mutants that are affected in carbon catabolite repression revealed that a 15-kDa protein was strongly overproduced in a ptsHI47T mutant . This protein was identified as EIIA of a mannose class phosphotransferase system (PTS) . A 7.1-kb DNA fragment containing the EIIA-encoding open reading frame and five other genes was sequenced . The first gene encodes a protein resembling the RpoN (  54)-dependent
Bacillus subtilis transcription activator LevR . The following
pentacistronic operon is oriented in the opposite direction and
encodes four proteins with strong similarity to the proteins of the
B . subtilis Lev-PTS and one protein of unknown function . The
genes present on the 7.1-kb DNA fragment were therefore called
levR and levABCDX . The levABCDX operon was induced
by fructose and mannose . No "–12, –24" promoter typical of
RpoN-dependent genes precedes the L . casei lev operon, and its
expression was therefore RpoN independent but required LevR .
Phosphorylation of LevR by P His-HPr
stimulates its activity, while phosphorylation by PEIIBLev
inhibits it . Disruption of the EIIBLev-encoding levB
gene therefore led to strong constitutive expression of the
lev operon, which was weaker in a strain carrying a ptsI mutation
preventing phosphorylation by both PEIIBLev
and PHis-HPr .
Expression of the L . casei lev operon is also subject to
P-Ser-HPr-mediated catabolite repression . The observed slow
phosphoenolpyruvate- and ATP-dependent phosphorylation of HPrI47T as
well as the slow phosphoryl group transfer from the mutant PHis-HPr
to EIIALev are assumed to be responsible for the elevated expression
of the lev operon in the ptsHI47T mutant .
Enhancement of Cry19Aa Mosquitocidal Activity against Aedes aegypti by Mutations in the Putative Loop Regions of Domain II. Mohd Amir F. Abdullah, 2004.Improvements in the mosquitocidal activity of Bacillus thuringiensis Cry19Aa were achieved by protein engineering of putative surface loop residues in domain II through rational design . The improvement of Aedes toxicity in Cry19Aa was 42,000-fold and did not affect its toxicity against Anopheles or Culex . The Global Transcriptional Response of Bacillus subtilis to Peroxide Stress Is Coordinated by Three Transcription Factors. John D. Helmann, 2003.Bacillus subtilis exhibits a complex adaptive response to low levels of peroxides . We used global transcriptional profiling to monitor the magnitude and kinetics of changes in the mRNA population after exposure to either hydrogen peroxide (H2O2) or tert-butyl peroxide (t-buOOH) . The peroxide stimulons could be largely accounted for by three regulons controlled by the PerR,  B, and OhrR transcription factors . Three members of the PerR regulon (katA, mrgA, and zosA) were strongly induced by H2O2 and weakly induced by t-buOOH . The remaining members of the PerR regulon were only modestly up-regulated by peroxide treatment . Overall, the magnitude of peroxide induction of PerR regulon genes corresponded well with the extent of derepression in a perR mutant strain . The
B regulon was activated by 58 µM H2O2 but not by 8 µM H2O2 and was strongly activated by either t-buOOH or, in a control experiment, tert-butyl alcohol . Apart from the
B regulon there was a single gene, ohrA, that was strongly and rapidly induced by t-buOOH exposure . This gene, controlled by the peroxide-sensing repressor OhrR, was not induced by any of the other conditions tested .
Angiotensin I-Converting-Enzyme-Inhibitory and Antibacterial Peptides from Lactobacillus helveticus PR4 Proteinase-Hydrolyzed Caseins of Milk from Six Species. F. Minervini, 2003.Sodium caseinates prepared from bovine, sheep, goat, pig, buffalo or human milk were hydrolyzed by a partially purified proteinase of Lactobacillus helveticus PR4 . Peptides in each hydrolysate were fractionated by reversed-phase fast-protein liquid chromatography . The fractions which showed the highest angiotensin I-converting-enzyme (ACE)-inhibitory or antibacterial activity were sequenced by mass spectrum and Edman degradation analyses . Various ACE-inhibitory peptides were found in the hydrolysates: the bovine  S1-casein (S1-CN) 24-47 fragment (f24-47), f169-193, and ß-CN f58-76; ovine
S1-CN f1-6 and
S2-CN f182-185 and f186-188; caprine ß-CN f58-65 and
S2-CN f182-187; buffalo ß-CN f58-66; and a mixture of three tripeptides originating from human ß-CN . A mixture of peptides with a C-terminal sequence, Pro-Gly-Pro, was found in the most active fraction of the pig sodium caseinate hydrolysate . The highest ACE-inhibitory activity of some peptides corresponded to the concentration of the ACE inhibitor (S)-N-(1-[ethoxycarbonyl]-3-phenylpropyl)-ala-pro maleate (enalapril) of 49.253 µg/ml (100 µmol/liter) . Several of the above sequences had features in common with other ACE-inhibitory peptides reported in the literature . The 50% inhibitory concentration (IC50) of some of the crude peptide fractions was very low (16 to 100 µg/ml) . Some identified peptides were chemically synthesized, and the ACE-inhibitory activity and IC50s were confirmed . An antibacterial peptide corresponding to ß-CN f184-210 was identified in human sodium caseinate hydrolysate . It showed a very large spectrum of inhibition against gram-positive and -negative bacteria, including species of potential clinical interest, such as Enterococcus faecium, Bacillus megaterium, Escherichia coli, Listeria innocua, Salmonella spp., Yersinia enterocolitica, and Staphylococcus aureus . The MIC for E . coli F19 was ca . 50 µg/ml . Once generated, the bioactive peptides were resistant to further degradation by proteinase of L . helveticus PR4 or by trypsin and chymotrypsin .
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