Spike Protein of COVID-19 Virus Reveals It’s Mechanism

COVID-19 causing coronaviruses have protein "spikes" on their surfaces that help the virus bind with the host receptors cells – first step of infection. Scientists have decoded the first detailed images of those spikes in their natural state, while still attached to the virus using cryogenic electron microscopy (cryo-EM) and computation techniques as per a study published in the journal Quarterly Reviews Biophysics Discovery. This serves as the critical step in designing therapeutic drugs and vaccines against the virus. "The advantage of doing it this way is that when you purify a spike protein and study it in isolation, you lose important biological context: How does it look in an intact virus particle? It could possibly have a different structure there," says Wah Chiu, a professor at DOE's SLAC National Accelerator Laboratory and Stanford University and senior author of the study.

There are seven infection causing strains of coronaviruses, among which four cause relatively mild illnesses and the other three - including SARS-CoV-2, the virus that causes COVID-19, being deadly. As the virulence of the virus based to the current pandemic, high enough level of biosafety controls are required in labs for studying the virus.

This explains the reason why present study incorporated milder form of the virus — NL63 for further investigation. The virus attaches to humans in a similar fashion to one causing qCOVID-19, thereby causing common cold symptoms. It accounts for 10% of human respiratory disease each year.

The spike protein structure:

The scientists purified NL63's spike proteins and flash-froze whole intact viruses into a glassy state thereby preserving the natural arrangement of their components. Digitally the spike protein copies were extracted to analyse them. The technique had better realistic outcome by skipping the prior formaldehyde fixation of virus.

“The structure we saw had exactly the same structure as it does on the virus surface, free of chemical artifacts. This had not been done before”, says co-author Jing Jin, an expert in the molecular biology of viruses at Vitalant Research Institute in San Francisco.

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Also the glycosylation process – how sugar molecules attach to the spike protein were unravelled. This mechanism plays an important role in the virus's life cycle and in its ability to evade the immune system.

Thus the study emphasizes on extracting the real essence of the mechanism by which the spike protein binds to receptors on human cells and it’s further activation.

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Source-Medindia