6s4q
scdSav(SASK) - Engineering Single-Chain Dimeric Streptavidin as Host for Artificial Metalloenzymes
Structural highlights
FunctionSAV_STRAV The biological function of streptavidin is not known. Forms a strong non-covalent specific complex with biotin (one molecule of biotin per subunit of streptavidin). Publication Abstract from PubMedThe biotin-streptavidin technology has been extensively exploited to engineer artificial metalloenzymes (ArMs) that catalyze a dozen different reactions. Despite its versatility, the homotetrameric nature of streptavidin (Sav) and the noncooperative binding of biotinylated cofactors impose two limitations on the genetic optimization of ArMs: (i) point mutations are reflected in all four subunits of Sav, and (ii) the noncooperative binding of biotinylated cofactors to Sav may lead to an erosion in the catalytic performance, depending on the cofactor:biotin-binding site ratio. To address these challenges, we report on our efforts to engineer a (monovalent) single-chain dimeric streptavidin (scdSav) as scaffold for Sav-based ArMs. The versatility of scdSav as host protein is highlighted for the asymmetric transfer hydrogenation of prochiral imines using [Cp*Ir(biot-p-L)Cl] as cofactor. By capitalizing on a more precise genetic fine-tuning of the biotin-binding vestibule, unrivaled levels of activity and selectivity were achieved for the reduction of challenging prochiral imines. Comparison of the saturation kinetic data and X-ray structures of [Cp*Ir(biot-p-L)Cl].scdSav with a structurally related [Cp*Ir(biot-p-L)Cl].monovalent scdSav highlights the advantages of the presence of a single biotinylated cofactor precisely localized within the biotin-binding vestibule of the monovalent scdSav. The practicality of scdSav-based ArMs was illustrated for the reduction of the salsolidine precursor (500 mM) to afford (R)-salsolidine in 90% ee and >17000 TONs. Monovalent scdSav thus provides a versatile scaffold to evolve more efficient ArMs for in vivo catalysis and large-scale applications. Breaking Symmetry: Engineering Single-Chain Dimeric Streptavidin as Host for Artificial Metalloenzymes.,Wu S, Zhou Y, Rebelein JG, Kuhn M, Mallin H, Zhao J, Igareta NV, Ward TR J Am Chem Soc. 2019 Oct 9;141(40):15869-15878. doi: 10.1021/jacs.9b06923. Epub, 2019 Sep 25. PMID:31509711[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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