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Molecular Basis of Iterative C–H Oxidation by TamI, a Multifunctional P450 Monooxygenase from the Tirandamycin Biosynthetic Pathway

preprint
submitted on 24.07.2020 and posted on 27.07.2020 by Sean A. Newmister, Kinshuk Raj Srivastava, Rosa V. Espinoza, Kersti Caddell Haatveit, Yogan Khatri, Rachel M. Martini, Marc Garcia-Borràs, Larissa M. Podust, Kendall N Houk, David H. Sherman
Biocatalysis offers an expanding and powerful strategy to construct and diversify complex molecules by C-H bond functionalization. Due to their high selectivity, enzymes have become an essential tool for C-H bond functionalization and offer complementary reactivity to small-molecule catalysts. Hemoproteins, particularly cytochromes P450, have proven effective for selective oxidation of unactivated C-H bonds. Previously, we reported the in vitro characterization of an oxidative tailoring cascade in which TamI, a multifunctional P450 functions co-dependently with the TamL flavoprotein to catalyze regio- and stereoselective hydroxylations and epoxidation to yield tirandamycin A and tirandamycin B. TamI follows a defined order including 1) C10 hydroxylation, 2) C11/C12 epoxidation, and 3) C18 hydroxylation. Here we present a structural, biochemical, and computational investigation of TamI to understand the molecular basis of its substrate binding, diverse reactivity, and specific reaction sequence. The crystal structure of TamI in complex with tirandamycin C together with molecular dynamics simulations and targeted mutagenesis suggest that hydrophobic interactions with the polyene chain of its natural substrate are critical for molecular recognition. QM/MM calculations and molecular dynamics simulations of TamI with variant substrates provided detailed information on the molecular basis of sequential reactivity, and pattern of regio- and stereo-selectivity in catalyzing the three-step oxidative cascade.

Funding

National Science Foundation CHE-1700982

National Institutes of Health R35GM118101

History

Email Address of Submitting Author

davidhs@umich.edu

Institution

University of Michigan

Country

USA

ORCID For Submitting Author

0000-0001-8334-3647

Declaration of Conflict of Interest

The authors declare no competing interests.

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