3N0H:
reference: Crystallographic analysis reveals a novel second binding site for trimethoprim in active site double mutants of human dihydrofolate reductase., Cody V, Pace J, Piraino J, Queener SF, J Struct Biol. 2011 Oct;176(1):52-9. Epub 2011 Jun 13. PMID: 21684339

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