3LB9:
reference: Circular permutation of Bacillus circulans xylanase: a kinetic and structural study., Reitinger S, Yu Y, Wicki J, Ludwiczek M, D'Angelo I, Baturin S, Okon M, Strynadka NC, Lutz S, Withers SG, McIntosh LP, Biochemistry. 2010 Mar 23;49(11):2464-74. PMID: 20163191

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