1MVK:
reference: Core mutations switch monomeric protein GB1 into an intertwined tetramer., Kirsten Frank M, Dyda F, Dobrodumov A, Gronenborn AM, Nat Struct Biol 2002 Nov;9(11):877-85. PMID: 12379842

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