5MK6:
reference: High resolution crystal structures of the receptor-binding domain of Clostridium botulinum neurotoxin serotypes A and FA., Davies JR, Hackett GS, Liu SM, Acharya KR, PeerJ. 2018 Mar 21;6:e4552. doi: 10.7717/peerj.4552. eCollection 2018. PMID: 29576992

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