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Figure 7
A proposed model of tthe gating-loop transition between the open, ready-to-close and closed conformations (upper panel) and the corresponding active site (lower panel). (a) The gating loop is fixed in the open state by hydrogen-bond interactions between Glu148 and Gly163 and between Thr187 and Ser164. PMP with the amino group pointing towards Lys274 has just been regenerated to restart the reaction. (b) The substrate (DAVA as the substrate analogue) interacts with Glu148 and Ser164 to interrupt the hydrogen-bond network between the gating loop and residues Glu148 and Thr187. Thus, the gating loop is released and ready to close. The PMP cofactor is tilted by 20–30°, with the amino group moving away from the catalytic lysine. (c) The gating loop moves to cover the active-site pocket during the catalytic process and Tyr302* forms a water-mediated hydrogen bond to Ser164. PMP is converted to PLP by forming a Schiff-base linkage to the lysine side chain. The asterisk indicates the residue from the neighbouring subunit.

ISSN: 2053-230X
Volume 72| Part 6| June 2016| Pages 448-456
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