Download MendeleyNonspecific Heme-Binding Cyclase, AbmU, Catalyzes [4 + 2] Cycloaddition during Neoabyssomicin Biosynthesis.
Li, Q., Ding, W., Tu, J., Chi, C., Huang, H., Ji, X., Yao, Z., Ma, M., Ju, J.(2020) ACS Omega 5: 20548-20557
- PubMed: 32832808
- DOI: https://doi.org/10.1021/acsomega.0c02776
- Primary Citation of Related Structures:
6LE0 - PubMed Abstract:
Diels-Alder (DA) [4 + 2]-cycloaddition reactions rank among the most powerful transformations in synthetic organic chemistry; biosynthetic examples, however, are few and far between. We report here a heme-binding cyclase, AbmU, that catalyzes an essential [4 + 2] cycloaddition during neoabyssomicin scaffold assembly. In vivo genetic and in vitro biochemical analyses strongly suggest that AbmU catalyzes an intramolecular and stereoselective [4 + 2] cycloaddition to form a spirotetronate skeleton from an acyclic substrate featuring both a terminal 1,3-diene and an exo-methylene group. Biochemical assays and X-ray diffraction analyses reveal that AbmU binds nonspecifically to a heme b cofactor and that this association does not play a catalytic role in AbmU catalysis. A detailed study of the AbmU crystal structure reveals a unique mode of substrate binding and reaction catalysis; His160 forms a H-bond with the C-1 carbonyl O-atom of the acyclic substrate, and the imidazole of the same amino acid directs the tetronate moiety of acyclic substrate toward the terminal Δ 10,11 , Δ 12,13 -diene moiety, thereby facilitating intramolecular DA chemistry. Our findings expand upon what is known about mechanistic diversities available to biosynthetic [4 + 2] cyclases and help to lay the foundation for the use of AbmU in possible industrial applications.
Organizational Affiliation:
CAS Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Key Laboratory of Marine Materia Medica, RNAM Center for Marine Microbiology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, 164 West Xingang Road, Guangzhou 510301, China.
