1NQN:
reference: Dimer-tetramer transition between solution and crystalline states of streptavidin and avidin mutants., Pazy Y, Eisenberg-Domovich Y, Laitinen OH, Kulomaa MS, Bayer EA, Wilchek M, Livnah O, J Bacteriol 2003 Jul;185(14):4050-6. PMID: 12837778

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