scholarly journals pH-dependence of the phospholipid interaction of diphtheria-toxin fragments

1985 ◽  
Vol 231 (1) ◽  
pp. 123-128 ◽  
Author(s):  
C Montecucco ◽  
G Schiavo ◽  
M Tomasi
Keyword(s):  
Diphtheria Toxin ◽  
Ph Dependence ◽  
Low Ph ◽  
Membrane Insertion ◽  
Ph Values ◽  
Egg Lecithin ◽  
A Chain ◽  
Lipid Interaction

Photoreactive phospholipids have been used to probe the lipid interaction of diphtheria toxin. Low pH values induce the membrane insertion of both the binding and enzymic fragments of the toxin. The efficiency of this process is much higher with asolectin than with egg lecithin (phosphatidylcholine)/cholesterol liposomes. The low-pH-induced interaction of the toxin fragments with the membrane hydrocarbon phase is more evident for the enzymic A-chain than for the binding B-chain, and it is fully reversed by returning the pH to neutrality.

scholarly journals pH-Dependent Interaction between C-Peptide and Phospholipid Bicelles

2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
Sofia Unnerståle ◽  
Lena Mäler
Keyword(s):  
Ph Dependence ◽  
Structural Rearrangement ◽  
Low Ph ◽  
Resonance Spectroscopy ◽  
Aggregation State ◽  
C Peptide ◽  
Ph Dependent ◽  
Lipid Interaction ◽  
Dependent Interaction

C-peptide is the connecting peptide between the A and B chains of insulin in proinsulin. In this paper, we investigate the interaction between C-peptide and phospholipid bicelles, by circular dichroism and nuclear magnetic resonance spectroscopy, and in particular the pH dependence of this interaction. The results demonstrate that C-peptide is largely unstructured independent of pH, but that a weak structural induction towards a short stretch of β-sheet is induced at low pH, corresponding to the isoelectric point of the peptide. Furthermore, it is demonstrated that C-peptide associates with neutral phospholipid bicelles as well as acidic phospholipid bicelles at this low pH. C-peptide does not undergo a large structural rearrangement as a consequence of lipid interaction, which indicates that the folding and binding are uncoupled. In vivo, local variations in environment, including pH, may cause C-peptide to associate with lipids, which may affect the aggregation state of the peptide.

scholarly journals Chemical synthesis and papain-catalysed hydrolysis of N-α-benzyloxycarbonyl-l-lysine p-nitroanilide

1985 ◽  
Vol 226 (2) ◽  
pp. 601-606 ◽  
Author(s):  
N E Mackenzie ◽  
J P G Malthouse ◽  
A I Scott
Keyword(s):  
Chemical Synthesis ◽  
Ph Dependence ◽  
Low Ph ◽  
Pka Values ◽  
Tetrahedral Intermediate ◽  
Ph Values ◽  
Km Value ◽  
Hydrolysis Of

The chemical synthesis of N-alpha-benzyloxycarbonyl-L-lysine p-nitroanilide (Z-Lys-pNA) is described in detail. The pH-dependence of the catalytic parameters kcat,' Km and kcat./Km for the papain-catalysed hydrolysis of Z-Lys-pNA are determined. kcat. and Km are pH-independent between pH 5 and pH 7.42, but the pH-dependence of kcat./Km is bell-shaped, decreasing at high and low pH values with pKa values of 7.97 and 4.40 respectively. The catalytic parameters and their pH-dependence are shown to be similar to those reported for other anilide substrates and it is concluded that the Km value of 0.01 mM previously reported [Angelides & Fink (1979) Biochemistry 18, 2355-2369] is incorrect. The possibility of accumulating a tetrahedral intermediate during the papain-catalysed hydrolysis of Z-Lys-pNA is discussed.

scholarly journals Role of Anions in Low pH-induced Translocation of Diphtheria Toxin

1989 ◽  
Vol 264 (19) ◽  
pp. 11367-11372 ◽  
Author(s):  
J Ø Moskaug ◽  
K Sandvig ◽  
S Olsnes
Keyword(s):  
Diphtheria Toxin ◽  
Low Ph

scholarly journals Adaptation of Lactobacillus plantarum IMDO 130201, a Wheat Sourdough Isolate, to Growth in Wheat Sourdough Simulation Medium at Different pH Values through Differential Gene Expression

2011 ◽  
Vol 77 (10) ◽  
pp. 3406-3412 ◽  
Author(s):  
Gino Vrancken ◽  
Luc De Vuyst ◽  
Tom Rimaux ◽  
Joke Allemeersch ◽  
Stefan Weckx
Keyword(s):  
Gene Expression ◽  
Lactobacillus Plantarum ◽  
Differential Gene Expression ◽  
Lipoteichoic Acid ◽  
Low Ph ◽  
Exponential Growth Phase ◽  
Cellular Mechanisms ◽  
Content Type ◽  
Ph Values ◽  
Differential Gene

ABSTRACTSourdough is a very competitive and challenging environment for microorganisms. Usually, a stable microbiota composed of lactic acid bacteria (LAB) and yeasts dominates this ecosystem. Although sourdough is rich in carbohydrates, thus providing an ideal environment for microorganisms to grow, its low pH presents a particular challenge. The nature of the adaptation to this low pH was investigated forLactobacillus plantarumIMDO 130201, an isolate from a laboratory wheat sourdough fermentation. Batch fermentations were carried out in wheat sourdough simulation medium, and total RNA was isolated from mid-exponential-growth-phase cultures, followed by differential gene expression analysis using a LAB functional gene microarray. At low pH values, an increased expression of genes involved in peptide and amino acid metabolism was found as well as that of genes involved in plantaricin production and lipoteichoic acid biosynthesis. The results highlight cellular mechanisms that allowL. plantarumto function at a low environmental pH.

scholarly journals pH-controlled hydrogen-bonding (Short Communication)

1974 ◽  
Vol 143 (3) ◽  
pp. 775-777 ◽  
Author(s):  
John L. Wood
Keyword(s):  
Hydrogen Bonding ◽  
Dissociation Constant ◽  
Small Proportion ◽  
Association Constant ◽  
Short Communication ◽  
Dibasic Acid ◽  
Ph Dependence ◽  
Ph Values ◽  
Conjugate Acid ◽  
Total Base

The pH-dependence of the degree of hydrogen-bonding between a base and its conjugate acid is considered. When only a small proportion of the total base is complexed, the amount complexed is proportional to (1+coshp)−1 where p=2.303 (pKa–pH), pKa being the dissociation constant of the conjugate acid. This represents sharp pH-dependence. As the proportion complexed increases, the curve broadens, eventually becoming flat-topped, with more than half the base complexed over the range of pH values pKa±logKC, approximately. (K is the complex association constant and C is the formal base concentration, including all forms.) There are similarities to the extent of mono-protonation of a dibasic acid.

scholarly journals Diphtheria toxin entry into cells is facilitated by low pH.

1980 ◽  
Vol 87 (3) ◽  
pp. 828-832 ◽  
Author(s):  
K Sandvig ◽  
S Olsnes
Keyword(s):  
Protein Synthesis ◽  
Toxic Effect ◽  
Diphtheria Toxin ◽  
Surface Membrane ◽  
Low Ph ◽  
Toxin A ◽  
Neutral Ph ◽  
Diphtheria Toxin A ◽  
Adsorptive Endocytosis

At neutral pH, NH4Cl and chloroquine protected cells against diphtheria toxin. A brief exposure of the cells to low pH (4.5-5.5) at 37 degrees completely abolished this protection. When, to cells preincubated with diphtheria toxin and NH4Cl, neutralizing amounts of anti-diphtheria toxin were added before the pH was lowered, the toxic effect was considerably reduced, but it was not completely abolished. A much stronger toxic effect was seen when antibodies were added immediately after incubation at low pH. Upon a short incubation with diphtheria toxin at low pH, the rate of protein synthesis in the cells decreased much faster than when the normal pH was maintained. The data suggest that, at low pH, diphtheria toxin (or its A fragment) penetrates directly through the surface membrane of the cell. The possibility is discussed that, when the medium has a neutral pH, the entry of diphtheria toxin involves adsorptive endocytosis and reduction of the pH in the vesicles possibly by fusion with lysosomes. Low pH did not facilitate the entry of the closely related toxins abrin, ricin, and modeccin.

scholarly journals Mechanism of Coagulation of Humic Acid in Presence of Metal Ion Coagulants at Low pH Values

1970 ◽  
Vol 73 (5) ◽  
pp. 874-878 ◽  
Author(s):  
Takao YOTSUYANAGI ◽  
Katsumi GOTO ◽  
Masaichi NAGAYAMA
Keyword(s):  
Humic Acid ◽  
Metal Ion ◽  
Low Ph ◽  
Ph Values
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