3GZK:
reference: Crystal Structures of A. acidocaldarius Endoglucanase Cel9A in Complex with Cello-Oligosaccharides: Strong -1 and -2 Subsites Mimic Cellobiohydrolase Activity., Eckert K, Vigouroux A, Lo Leggio L, Morera S, J Mol Biol. 2009 Aug 31. PMID: 19729024

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