4XKB:
reference: Crystal Structures of GUN4 in Complex with Porphyrins., Chen X, Pu H, Wang X, Long W, Lin R, Liu L, Mol Plant. 2015 Jul 6;8(7):1125-7. doi: 10.1016/j.molp.2015.04.013. Epub 2015 May, 7. PMID: 25958236

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