Please use this identifier to cite or link to this item: http://hdl.handle.net/20.500.12779/3850
Title: Tyrosine 65 is photolabeled by 8-azidoadenine and 8-azidoadenosine at the NAD binding site of diphtheria toxin.
Authors: Papini, E
Santucci, Annalisa 
Schiavo, G
Domenighini, M
Neri, Paolo
Rappuoli, R
Montecucco, C.
Issue Date: 1991
Project: None 
Journal: THE JOURNAL OF BIOLOGICAL CHEMISTRY
Abstract: 
8-Azidoadenine and 8-azidoadenosine, two photoactivatable derivatives of adenine and adenosine, are competitive inhibitors of diphtheria toxin of similar potency with respect to their parent compounds. On irradiation, the two tritium-labeled photoactivatable azidoadenines bind covalently and specifically to an enzymic fragment of diphtheria toxin that is known to bind to NAD. This photolabeling is protected by the enzyme substrate NAD. The radiolabeled protein was fragmented, and the radioactive fragments were sequenced. Tyr-65 is labeled specifically by both photoreagents, and its labeling was reduced strongly when NAD was present during irradiation. Labeling is also reduced strongly by adenine, adenosine, and nicotinamide. These results suggest that Tyr-65 is at the NAD binding site of diphtheria toxin and that the competitive inhibitors adenine, adenosine, and nicotinamide bind to the same portion of the catalytic center of the toxin.
Description: 
24700
URI: http://hdl.handle.net/20.500.12779/3850
ISSN: 0021-9258
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