5ECC:
reference: Crystal Structures of Trimethoprim-Resistant DfrA1 Rationalize Potent Inhibition by Propargyl-Linked Antifolates., Lombardo MN, G-Dayanandan N, Wright DL, Anderson AC, ACS Infect Dis. 2016 Feb 12;2(2):149-56. doi: 10.1021/acsinfecdis.5b00129. Epub, 2016 Jan 4. PMID: 27624966

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