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Blake-Hedges JM, Pereira JH, Cruz-Morales P, Thompson MG, Barajas JF, Chen J, Krishna RN, Chan LJG, Nimlos D, Alonso-Martinez C, Baidoo EEK, Chen Y, Gin JW, Katz L, Petzold CJ, Adams PD, Keasling JD. Structural Mechanism of Regioselectivity in an Unusual Bacterial Acyl-CoA Dehydrogenase. J Am Chem Soc 2020; 142:835-846. [PMID: 31793780 DOI: 10.1021/jacs.9b09187] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Terminal alkenes are easily derivatized, making them desirable functional group targets for polyketide synthase (PKS) engineering. However, they are rarely encountered in natural PKS systems. One mechanism for terminal alkene formation in PKSs is through the activity of an acyl-CoA dehydrogenase (ACAD). Herein, we use biochemical and structural analysis to understand the mechanism of terminal alkene formation catalyzed by an γ,δ-ACAD from the biosynthesis of the polyketide natural product FK506, TcsD. While TcsD is homologous to canonical α,β-ACADs, it acts regioselectively at the γ,δ-position and only on α,β-unsaturated substrates. Furthermore, this regioselectivity is controlled by a combination of bulky residues in the active site and a lateral shift in the positioning of the FAD cofactor within the enzyme. Substrate modeling suggests that TcsD utilizes a novel set of hydrogen bond donors for substrate activation and positioning, preventing dehydrogenation at the α,β position of substrates. From the structural and biochemical characterization of TcsD, key residues that contribute to regioselectivity and are unique to the protein family were determined and used to identify other putative γ,δ-ACADs that belong to diverse natural product biosynthetic gene clusters. These predictions are supported by the demonstration that a phylogenetically distant homologue of TcsD also regioselectively oxidizes α,β-unsaturated substrates. This work exemplifies a powerful approach to understand unique enzymatic reactions and will facilitate future enzyme discovery, inform enzyme engineering, and aid natural product characterization efforts.
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Affiliation(s)
- Jacquelyn M Blake-Hedges
- Department of Chemistry , University of California , Berkeley , California 94720 , United States.,Joint BioEnergy Institute , Emeryville , California 94608 , United States.,Biological Systems and Engineering Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
| | - Jose Henrique Pereira
- Joint BioEnergy Institute , Emeryville , California 94608 , United States.,Molecular Biophysics and Integrated Bioimaging , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
| | - Pablo Cruz-Morales
- Joint BioEnergy Institute , Emeryville , California 94608 , United States.,Biological Systems and Engineering Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
| | - Mitchell G Thompson
- Joint BioEnergy Institute , Emeryville , California 94608 , United States.,Biological Systems and Engineering Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States.,Department of Plant and Microbial Biology , University of California-Berkeley , Berkeley , California 94720 , United States
| | - Jesus F Barajas
- Joint BioEnergy Institute , Emeryville , California 94608 , United States.,Biological Systems and Engineering Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States.,Department of Plant and Microbial Biology , University of California-Berkeley , Berkeley , California 94720 , United States
| | - Jeffrey Chen
- Department of Chemistry , University of California , Berkeley , California 94720 , United States
| | - Rohith N Krishna
- Department of Chemistry , University of California , Berkeley , California 94720 , United States
| | - Leanne Jade G Chan
- Joint BioEnergy Institute , Emeryville , California 94608 , United States.,Biological Systems and Engineering Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
| | - Danika Nimlos
- Department of Chemistry , University of California , Berkeley , California 94720 , United States
| | - Catalina Alonso-Martinez
- Department of Chemistry , University of California , Berkeley , California 94720 , United States
| | - Edward E K Baidoo
- Joint BioEnergy Institute , Emeryville , California 94608 , United States.,Biological Systems and Engineering Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
| | - Yan Chen
- Joint BioEnergy Institute , Emeryville , California 94608 , United States.,Biological Systems and Engineering Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States.,Department of Energy Agile BioFoundry , Emeryville , California 94608 , United States
| | - Jennifer W Gin
- Joint BioEnergy Institute , Emeryville , California 94608 , United States.,Biological Systems and Engineering Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States.,Department of Energy Agile BioFoundry , Emeryville , California 94608 , United States
| | - Leonard Katz
- Joint BioEnergy Institute , Emeryville , California 94608 , United States.,QB3 Institute , University of California-Berkeley , Emeryville , California 94608 , United States
| | - Christopher J Petzold
- Joint BioEnergy Institute , Emeryville , California 94608 , United States.,Biological Systems and Engineering Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States.,Department of Energy Agile BioFoundry , Emeryville , California 94608 , United States
| | - Paul D Adams
- Joint BioEnergy Institute , Emeryville , California 94608 , United States.,Biological Systems and Engineering Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States.,Molecular Biophysics and Integrated Bioimaging , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
| | - Jay D Keasling
- Joint BioEnergy Institute , Emeryville , California 94608 , United States.,Biological Systems and Engineering Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States.,QB3 Institute , University of California-Berkeley , Emeryville , California 94608 , United States.,Department of Chemical & Biomolecular Engineering, Department of Bioengineering , University of California-Berkeley , Berkeley , California 94720 , United States.,Novo Nordisk Foundation Center for Biosustainability , Technical University Denmark , DK2970 Horsholm , Denmark.,Center for Synthetic Biochemistry , Shenzhen Institutes for Advanced Technologies , Shenzhen 518055 , P. R. China
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