1P43:
reference: Reverse protonation is the key to general acid-base catalysis in enolase., Sims PA, Larsen TM, Poyner RR, Cleland WW, Reed GH, Biochemistry 2003 Jul 15;42(27):8298-306. PMID: 12846578

This OCA Structure page
uses Jmol, developed by the Jmol Development Team (documentation).