2I4C:
reference: The structure of a cyanobacterial bicarbonate transport protein, CMPA., Koropatkin NM, Koppenaal DW, Pakrasi HB, Smith TJ, J Biol Chem. 2006 Nov 22;. PMID: 17121816

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