4FRL:
reference: pH-induced conformational changes in human ABO(H) blood group glycosyltransferases confirm the importance of electrostatic interactions in formation of the semi-closed state., Johal AR, Blackler RJ, Alfaro JA, Schuman B, Borisova S, Evans SV, Glycobiology. 2013 Nov 20. PMID: 24265507

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