Specific binding of nucleotides and NAD+ to Clostridium difficile toxin A

Abstract
Binding of nucleotides, a tetrapolyphosphate, and NAD+ to purified toxin A of Clostridium difficile was determined by monitoring changes in intrinsic fluorescence following excitation at 280 nm, and recording emissions at 340 nm. Binding was specific for concentration over the range 5 to 100 μM for ATP, GTP, and their respective non‐hydrolysable analogues AMP‐PNP and Gpp(NH)p, tetrapolyphosphate and NAD+.