1X12:
reference: Completely buried, non-ion-paired glutamic acid contributes favorably to the conformational stability of pyrrolidone carboxyl peptidases from hyperthermophiles., Kaushik JK, Iimura S, Ogasahara K, Yamagata Y, Segawa S, Yutani K, Biochemistry. 2006 Jun 13;45(23):7100-12. PMID: 16752900

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