1HTL:
reference: Mutation of a buried residue causes loss of activity but no conformational change in the heat-labile enterotoxin of Escherichia coli., Merritt EA, Sarfaty S, Pizza M, Domenighini M, Rappuoli R, Hol WG, Nat Struct Biol 1995 Apr;2(4):269-72. PMID: 7796260

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