3OSR:
reference: A genetically encoded, high-signal-to-noise maltose sensor., Marvin JS, Schreiter ER, Echevarria IM, Looger LL, Proteins. 2011 Nov;79(11):3025-36. doi: 10.1002/prot.23118. PMID: 21989929

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