6DFR:
reference: Crystal structures of Escherichia coli dihydrofolate reductase: the NADP+ holoenzyme and the folate.NADP+ ternary complex. Substrate binding and a model for the transition state., Bystroff C, Oatley SJ, Kraut J, Biochemistry 1990 Apr 3;29(13):3263-77. PMID: 2185835

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