3D modelling shows novel coronavirus binds to human cells better than SARS

TORONTO — A new study that uses 3D modelling to compare the novel coronavirus with SARS shows that it can bind to human cells more strongly than its predecessor due to a structural mutation, which researchers say could be key knowledge in the search for a vaccine.

The study, published this week in the scientific journal Nature, was conducted by researchers from the University of Minnesota, and compared the novel coronavirus (referred to in the study as SARS CoV-2) to the structure and behaviour of SARS, which belongs to the same family of coronaviruses.

The research looks at how structural mutations allowed the novel coronavirus to spread so far and so fast.

The way that coronaviruses infect humans is by latching onto receptors — specific proteins in human cells.

The way SARS (referred to in the study at SARS-CoV) attaches through receptors has been studied before. A “spike” protein on the surface of the virus is what allows it to bind to human cells. Spike proteins collected around the edge of the virus are what give coronaviruses their distinct “corona” — or crown-like — appearance.

The novel coronavirus, which causes the disease known as COVID-19, also uses spike proteins to bind to receptors in human cells — specifically, receptors found on lung cells.

“The receptor ‘receives’ the virus, much as a lock receives a key,” explains a University of Minnesota press release on the research.

Although studies have already been done to model the novel coronavirus and look at how it impacts the human body, this study is the first to use “x-ray crystallography,” according to the press release. This technique, which is considered the best way to determine the structure of proteins and macromolecules, allows researchers to build a 3D map of the virus and the receptors it is targeting within humans.

The new 3D modelling of the novel coronavirus shows that this new virus has developed a molecular “ridge” in its spike proteins, which allows it to bind more securely to human cells than its predecessor SARS did.

The study says that compared with SARS, the novel coronavirus’ spike protein “forms a larger binding interface and more contacts with” the specific receptors in human cells that it targets.

Put more plainly, this structural difference is one factor that allows the novel coronavirus to attach itself to human cells to infect people faster and stronger than SARS ever could.

Investigating exactly how the novel coronavirus binds to receptors on human cells is key to understanding how to create a vaccine or anti-viral medications.

“In general, by learning what structural features of viral proteins are most important in establishing contact with human cells, we can design drugs that seek them out and block their activity — like jamming their radar,” said Fang Li in the press release. Li is a professor in the Department of Veterinary and Biomedical Sciences at the University of Minnesota, and the research lead for the team.

If a vaccine could be made that binds more strongly to the receptors in human cells that the virus targets, the vaccine would essentially beat the virus to the punch, blocking those receptors and leaving the virus no way to infect the person in question.

The study also compared the structure of the novel coronavirus with coronaviruses found in bats and pangolins in an attempt to get a greater understanding of a possible animal connection.

The research found structural similarities in receptor recognition between bat coronaviruses and the novel coronavirus that impacts humans, adding support to a theory that bats could have been a start-point for the virus.

They also investigated coronaviruses in pangolins and found that there was evidence that they could potentially have served as an intermediary hosts. However, researchers cautioned that there is still much unknown about how the virus moved from animals to humans, and that their results don’t prove a definite pathway for the virus.

“Many other factors determine the cross-species transmission of coronaviruses, and the above analysis will need to be verified experimentally,” the study cautions.

In its conclusions, the study says that this new information could impact “structure-based intervention strategies.

“This study can guide the development and optimization of these antibody drugs,” the study reads.

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