A Virus-Binding Hot Spot on Human Angiotensin-Converting Enzyme 2 Is Critical for Binding of Two Different Coronaviruses

Department of Pharmacology, University of Minnesota Medical School, Minneapolis, MN 55455, USA.
Journal of Virology (Impact Factor: 4.44). 03/2011; 85(11):5331-7. DOI: 10.1128/JVI.02274-10
Source: PubMed


How viruses evolve to select their receptor proteins for host cell entry is puzzling. We recently determined the crystal structures of NL63 coronavirus (NL63-CoV) and SARS coronavirus (SARS-CoV) receptor-binding domains (RBDs), each complexed with their common receptor, human angiotensin-converting enzyme 2 (hACE2), and proposed the existence of a virus-binding hot spot on hACE2. Here we investigated the function of this hypothetical hot spot using structure-guided biochemical and functional assays. The hot spot consists of a salt bridge surrounded by hydrophobic tunnel walls. Mutations that disturb the hot spot structure have significant effects on virus/receptor interactions, revealing critical energy contributions from the hot spot structure. The tunnel structure at the NL63-CoV/hACE2 interface is more compact than that at the SARS-CoV/hACE2 interface, and hence RBD/hACE2 binding affinities are decreased either by NL63-CoV mutations decreasing the tunnel space or by SARS-CoV mutations increasing the tunnel space. Furthermore, NL63-CoV RBD inhibits hACE2-dependent transduction by SARS-CoV spike protein, a successful application of the hot spot theory that has the potential to become a new antiviral strategy against SARS-CoV infections. These results suggest that the structural features of the hot spot on hACE2 were among the driving forces for the convergent evolution of NL63-CoV and SARS-CoV.

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    • "As civet (c) ACE2 displayed affinity for both human (Tor2 and GD03) and civet SARS-CoV isolates (Sz02 and Gd05), while human (h) ACE2 preferentially bound the S protein RBD of human isolates, biochemical studies were performed to define mutations influencing RBD affinity (Li, 2008; Wu et al., 2012, 2011; Li et al., 2005b). These studies identified two regions of interaction between the S protein RBD and ACE2 at which mutations evolved to accommodate a switch in preference from cACE2 to hACE2 (Li, 2008; Wu et al., 2012, 2011). The two regions were designated hotspot 31 and hotspot 353. "
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