# Toxin \(\zeta\) Reduces the ATP and Modulates the Uridine Diphosphate-N-acetylglucosamine Pool
## 2 Results
### Reaction Mechanism
#### 2.6.1 One Step Phosphotransferase Reaction
\begin{table}
\begin{tabular}{c c c} \hline \hline
**ATP-P\(\gamma\) Near to UNAG-O3\({}^{\prime}\)** & **\(\Delta\)G\({}^{\ddagger}\) (Kcal/mol)** & **\(\Delta\)G\({}^{\circ}\) (Kcal/mol)** \\ \hline ATP + Mg\({}^{2+}\) + UNAG (H\({}_{2}\)O) & 13.81 & 33.63 \\ \(\zeta\) + ATP + Mg\({}^{2+}\) + UNAG (H\({}_{2}\)O) & 18.28 & 10.76 \\ ATP + Mg\({}^{2+}\) + UNAG (NaCl) & 7.28 & \(-\)17.84 \\ \(\zeta\) + ATP + Mg\({}^{2+}\) + UNAG (NaCl) & 2.98 & \(-\)4.62 \\ \hline
**ATP-P\(\gamma\) Far from UNAG-O3\({}^{\prime}\)** & **\(\Delta\)G\({}^{\ddagger}\) (Kcal/mol)** & **\(\Delta\)G\({}^{\circ}\) (Kcal/mol)** \\ \hline ATP + Mg\({}^{2+}\) + UNAG (water) & 5.45 & \(-\)0.61 \\ ATP + Mg\({}^{2+}\) + UNAG + H\({}_{2}\)O (water) & 23.98 & 16.05 \\ \(\zeta\) + ATP + Mg\({}^{2+}\) + UNAG (water, tot) & 79.35 & 14.5 \\ \(\zeta\) + ATP + Mg\({}^{2+}\) + UNAG (water, react) & 16.56 & \(-\)48.29 \\ ATP + Mg\({}^{2+}\) + UNAG (NaCl) & 161.57 & 95.3 \\ ATP + Mg\({}^{2+}\) + UNAG + H\({}_{2}\)O (NaCl) & 23.16 & 9.77 \\ \(\zeta\) + ATP + Mg\({}^{2+}\) + UNAG (NaCl) & 38.64 & 8.57 \\ \hline
**ATP-P\(\gamma\) Far from UNAG-O3\({}^{\prime}\) (two steps)** & **\(\Delta\)G\({}^{\ddagger}\) (Kcal/mol)** & **\(\Delta\)G\({}^{\circ}\) (Kcal/mol)** \\ \hline \hline \(\zeta\) + ATP + Mg\({}^{2+}\) + H\({}_{2}\)O\({}^{1059}\) + UNAG (water, step 1) & 9.61 & 0.68 \\ \(\zeta\) + ADP + Mg\({}^{2+}\) + P\({}_{1}\)\({}^{1059}\) + UNAG (water, step 2) & 25.2 & \(-\)9 \\ \(\zeta\) + ATP + Mg\({}^{2+}\) + H\({}_{2}\)O\({}^{259}\) + UNAG (water, step 1) & 36.14 & 2.29 \\ \(\zeta\) + ADP + Mg\({}^{2+}\) + P\({}_{1}\)\({}^{259}\) + UNAG (water, step 2) & 24.32 & 49.23 \\ \(\zeta\) + ATP + Mg\({}^{2+}\) + H\({}_{2}\)O\({}^{273}\) + UNAG (water, step 1) & 8.81 & \(-\)11.05 \\ \(\zeta\) + ADP + Mg\({}^{2+}\) + P\({}_{1}\)\({}^{273}\) + UNAG (water, step 2) & 33.03 & 45.31 \\ \(\zeta\) + ATP + Mg\({}^{2+}\) + H\({}_{2}\)O\({}^{3646}\) + UNAG (water, step 1) & 7.35 & \(-\)14.44 \\ \(\zeta\) + ADP + Mg\({}^{2+}\) + P\({}_{3}\)\({}^{3646}\) + UNAG (water, step 2) & 44.52 & \(-\)22.06 \\ \(\zeta\) + ATP + Mg\({}^{2+}\) + H\({}_{2}\)O\({}^{2024}\) + UNAG (NaCl, step 1) & 2 & \(-\)16.86 \\ \(\zeta\) + ADP + Mg\({}^{2+}\) + P\({}_{1}\)\({}^{204}\) + UNAG (NaCl, step 2) & 54.53 & 52.21 \\ \(\zeta\) + ATP + Mg\({}^{2+}\) + H\({}_{2}\)O\({}^{2637}\) + UNAG (NaCl, step 1) & 4 & \(-\)9.12 \\ \(\zeta\) + ADP + Mg\({}^{2+}\) + P\({}_{1}\)\({}^{2637}\) + UNAG (NaCl, step 2) & 46.12 & 47.54 \\ \(\zeta\) + ATP + Mg\({}^{2+}\) + H\({}_{2}\)O\({}^{4589}\) + UNAG (NaCl, step 1) & 2.77 & 18.74 \\ \(\zeta\) + ADP + Mg\({}^{2+}\) + P\({}_{1}\)\({}^{45899}\) + UNAG (NaCl, step 2) & 47.22 & 39.47 \\ \hline \hline \end{tabular} \(\Delta\)G\({}^{\ddagger}\): activation energy (Kcal/mol) and \(\Delta\)G\({}^{\circ}\): reaction energy (Kcal/mol) of modeled reactions. Near: models starting from a position with P\(\gamma\) near (-3.5 Å) O3’. Far: models starting from a conformation with P\(\gamma\) far (-7 Å) from O3’. Water and 140 mM NaCl indicate models simulated in water and NaCl counterions. Tot: total energy change (including entropic changes). React: actual reaction energy (after ligand approximation). Step 1: model of the reaction ATP + H\({}_{2}\)O \(\rightarrow\) ADP + P\({}_{1}\). Step 2: model of the reaction P\({}_{1}\) + UNAG \(\rightarrow\) UNAG-P.  
\end{table} 
Table 3: Alternative endothermic phosphorylation. In the presence of toxin \(\zeta\) and NaCl, several Na\({}^{+}\) ions cluster close to the triphosphate chain of ATP, balancing its negative charges, and the reaction proceeded with a lowering of the activation energy to \(\Delta\)E\({}^{\ddagger}\) = 3.0 and of total energy release, \(\Delta\)E\({}^{\circ}\) = \(-\)4.6 (Table 3). When the simulations started with both ligands in distant positions, the reaction mechanisms were less clear. The energy landscape varied considerably, but it was generally unfavorable (Movie S1).