 | Acta Crystallographica Section D Acta Crystallographica Section D BIOLOGICAL CRYSTALLOGRAPHY |
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![[Figure 3]](hv5073fig3mag.jpg)
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Figure 3
Changes in protonation states tune the binding mode of 2′P-ADP-ribose. (a) At pH 7.7 both the 2′-phosphate group of the ligand and Glu256 will be negatively charged, carrying a −2 and a −1 charge, respectively. Their interaction would be highly unfavourable. The ligand binds in the same orientation observed for NADP+, anchoring the 2′-phosphate close to Arg31 and hydrogen bonding to Glu256 via the terminal ribose. (b) Binding mode observed in the KPR–2′P-ADP-ribose crystal structure reported here. At pH 4.5 the 2′-phosphate becomes protonated (pK = 6.5) carrying a single negative charge. Glu256 is likely to protonate, allowing a favourable hydrogen bond to the 2′-phosphate group. |
![[Figure 3]](hv5073fig3.jpg)
| BIOLOGICAL CRYSTALLOGRAPHY |
ISSN: 1399-0047
