scholarly journals Unusual conformation of nicotinamide adenine dinucleotide (NAD) bound to diphtheria toxin: A comparison with NAD bound to the oxidoreductase enzymes

2008 ◽  
Vol 6 (10) ◽  
pp. 2084-2096 ◽  
Author(s):  
Charles E. Bell ◽  
Todd O. Yeates ◽  
David Eisenberg
Keyword(s):  
Nicotinamide Adenine Dinucleotide ◽  
Diphtheria Toxin ◽  
Nicotinamide Adenine ◽  
Toxin A ◽  
Diphtheria Toxin A ◽  
Oxidoreductase Enzymes

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.

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