3I3E:
reference: Role of Met-542 as a guide for the conformational changes of Phe-601 that occur during the reaction of β-galactosidase (Escherichia coli)., Dugdale ML, Dymianiw DL, Minhas BK, D'Angelo I, Huber RE, Biochem Cell Biol. 2010 Oct;88(5):861-9. PMID: 20921997

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