New Coronavirus Variant: What Is The Spike Protein And Why Are Mutations On It Important?

Francesca Benson MSci 28 Dec 2020, 17:24

The Conversation

The emergence of a new variant of coronavirus has sparked renewed interest in the part of the virus known as the spike protein.

The new variant carries several peculiar changes to the spike protein when compared to other closely related variants – and that’s one of the reasons why it’s more concerning than other, harmless changes to the virus we have observed before. The new mutations may alter the biochemistry of the spike and could affect how transmissible the virus is.

The spike protein is also the basis of current COVID-19 vaccines, which seek to generate an immune response against it. But what exactly is the spike protein and why is it so important?

Diagram showing the structure of the SARS-CoV-2 coronavirus molecule in full and in section.
The SARS-CoV-2 coronavirus molecule. Klerka/Shutterstock.com

Cell invaders

In the world of parasites, many bacterial or fungal pathogens can survive on their own without a host cell to infect. But viruses can’t. Instead, they have to get inside cells in order to replicate, where they use the cell’s own biochemical machinery to build new virus particles and spread to other cells or individuals.

Our cells have evolved to ward off such intrusions. One of the major defences cellular life has against invaders is its outer coating, which is composed of a fatty layer that holds in all the enzymes, proteins and DNA that make up a cell. Due to the biochemical nature of fats, the outer surface is highly negatively charged and repellent. Viruses must traverse this barrier to gain access to the cell.

A diagram showing the mechanism by which SARS-CoV-2 is able to enter cells and reproduce.
How SARS-CoV-2 gets into cells and reproduces. Pišlar A, Mitrović A, Sabotič J, Pečar Fonović U, Perišić Nanut M, Jakoš T, et al, PLoS Pathog 16(11)CC BY
Like cellular life, coronaviruses themselves are surrounded by a fatty membrane known as an envelope. In order to gain entry to the inside of the cell, enveloped viruses use proteins (or glycoproteins as they are frequently covered in slippery sugar molecules) to fuse their own membrane to that of cells’ and take over the cell.

The spike protein of coronaviruses is one such viral glycoprotein. Ebola viruses have one, the influenza virus has two, and herpes simplex virus has five.

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