journals.plos.org
Cetacean coronavirus spikes highlight S glycoprotein structural plasticity
Author summary Coronaviruses are well known for their ability to jump between species, a process driven mainly by the spike protein on their surface. In this study, we examined spike proteins from coronaviruses found in marine mammals (whales and dolphins) to better understand how these viruses evolve and interact with their hosts. Using structural biology and mass spectrometry, we discovered several unusual features of the cetacean spike proteins. These spikes contain an extra domain within their receptor-binding region that resembles cupin proteins, assemble into trimers in a novel way that hides the receptor-binding domains, and show clusters of sugars (O-linked glycans) near the sites thought to interact with host receptors. These distinctive features suggest that cetacean coronaviruses may use a different entry mechanism, in which the extra domain acts as a switch to reveal the hidden receptor-binding regions. Such a mechanism could affect which species these viruses can infect, how easily they cross species barriers, and how they evade the immune system. Our findings emphasize the structural diversity and modularity of coronavirus spike proteins, highlight the unique adaptations of coronaviruses in marine mammals, and provide insight into their potential to give rise to new diseases in other species.
