The coronavirus S-protein mediates receptor binding and fusion of the viral and host cell membranes. In HCoV-229E, its receptor binding domain (RBD) shows extensive sequence variation but how S-protein function is maintained is not understood. Reported are the X-ray crystal structures of Class III-V RBDs in complex with human aminopeptidase N (hAPN), as well as the electron cryomicroscopy structure of the 229E S-protein. The structures show that common core interactions define the specificity for hAPN and that the peripheral RBD sequence variation is accommodated by loop plasticity. The results provide insight into immune evasion and the cross-species transmission of 229E and related coronaviruses. We also find that the 229E S-protein can expose a portion of its helical core to solvent. This is undoubtedly facilitated by hydrophilic subunit interfaces that we show are conserved among coronaviruses. These interfaces likely play a role in the S-protein conformational changes associated with membrane fusion.
The X-ray diffraction data and X-ray crystal structures have been deposited in PDB under accession codes 6U7E, 6U7F and 6U7G. The cryo-EM map has been deposited in EMDB under accession code EMD-20668. The cryo-EM structure has been deposited in PDB under accession code 6U7H.
X-ray diffraction data and X-ray crystal structuresProtein Data Bank, 6U7E.
X-ray diffraction data and X-ray crystal structuresProtein Data Bank, 6U7F.
X-ray diffraction data and X-ray crystal structuresProtein Data Bank, 6U7G.
cryo-EM structureProtein Data Bank, 6U7H.
cryo-EM mapElectron Microsopy Data Bank, EMD-20668.
- James M Rini
- John L Rubinstein
- Pierre J Talbot
- John L Rubinstein
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
- Pamela J Bjorkman, California Institute of Technology, United States
© 2019, Li et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
Kinase inhibitors are successful therapeutics in the treatment of cancers and autoimmune diseases and are useful tools in biomedical research. However, the high sequence and structural conservation of the catalytic kinase domain complicates the development of selective kinase inhibitors. Inhibition of off-target kinases makes it difficult to study the mechanism of inhibitors in biological systems. Current efforts focus on the development of inhibitors with improved selectivity. Here, we present an alternative solution to this problem by combining inhibitors with divergent off-target effects. We develop a multicompound-multitarget scoring (MMS) method that combines inhibitors to maximize target inhibition and to minimize off-target inhibition. Additionally, this framework enables optimization of inhibitor combinations for multiple on-targets. Using MMS with published kinase inhibitor datasets we determine potent inhibitor combinations for target kinases with better selectivity than the most selective single inhibitor and validate the predicted effect and selectivity of inhibitor combinations using in vitro and in cellulo techniques. MMS greatly enhances selectivity in rational multitargeting applications. The MMS framework is generalizable to other non-kinase biological targets where compound selectivity is a challenge and diverse compound libraries are available.
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