4RL1:
reference: Structural and Functional Analysis of the Loading Acyltransferase from Avermectin Modular Polyketide Synthase., Wang F, Wang Y, Ji J, Zhou Z, Yu J, Zhu H, Su Z, Zhang L, Zheng J, ACS Chem Biol. 2015 Jan 22. PMID: 25581064

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