Photoaffinity labeling of diphtheria toxin fragment A with NAD: structure of the photoproduct at position 148.
Irradiation of mixtures of diphtheria toxin fragment A and [carbonyl-14C]NAD with UV light (253.7 nm) is known to induce efficient transfer of the radiolabel to position 148, corresponding to glutamic acid in the unmodified protein. Here we report the structure of the photoproduct at position 148, as determined by chemical and photochemical methods, fast-atom-bombardment mass spectrometry, and nuclear magnetic resonance. The photoproduct [an alpha-amino-gamma-(6-nicotin-amidyl)butyric acid residue] contains the entire nicotinamide moiety of NAD linked via its number 6 carbon to the decarboxylated gamma-methylene carbon of Glu-148. No portion of the ADP-ribosyl group of NAD is present. These findings are consistent with the idea that Glu-148 lies at or near the catalytic center of diphtheria toxin.
D036002:ADP Ribose Transferases; D000345:Affinity Labels; D001427:Bacterial Toxins; D001665:Binding Sites; D004167:Diphtheria Toxin / Q000032:analysis* / Q000528:radiation effects; D005098:Exotoxins / Q000032:analysis / Q000528:radiation effects; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D009243:NAD / Q000032:analysis*; D010446:Peptide Fragments / Q000032:analysis* / Q000528:radiation effects; D010777:Photochemistry; D011487:Protein Conformation; D014466:Ultraviolet Rays; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A
D036002:ADP Ribose Transferases; D000345:Affinity Labels; D001427:Bacterial Toxins; D004167:Diphtheria Toxin; D005098:Exotoxins; D009243:NAD; D010446:Peptide Fragments; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A; C029795:diphtheria toxin fragment A