![]() ![]() The spike is also involved in other processes like assembly, structural stability and immune evasion. One of these functional units binds to a protein on the surface of our cells called ACE2, triggering uptake of the virus particle and eventually membrane fusion. There are estimated to be roughly 26 spike trimers per virus. The spike protein of SARS-CoV-2 is stuck on the roughly spherical viral particle, embedded within the envelope and projecting out into space, ready to cling on to unsuspecting cells. The spike protein is made up of different sections that perform different functions. The spike can be subdivided into distinct functional units, known as domains, which fulfil different biochemical functions of the protein, such as binding to the target cell, fusing with the membrane, and allowing the spike to sit on the viral envelope. Spike proteins like to stick together and three separate spike molecules bind to each other to form a functional “trimeric” unit. The spike protein is composed of a linear chain of 1,273 amino acids, neatly folded into a structure, which is studded with up to 23 sugar molecules. Ebola viruses have one, the influenza virus has two, and herpes simplex virus has five. The spike protein of coronaviruses is one such viral glycoprotein. 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. Like cellular life, coronaviruses themselves are surrounded by a fatty membrane known as an envelope. ![]() ![]() Pišlar A, Mitrović A, Sabotič J, Pečar Fonović U, Perišić Nanut M, Jakoš T, et al, PLoS Pathog 16(11), CC BY How SARS-CoV-2 gets into cells and reproduces. Viruses must traverse this barrier to gain access to the cell. Due to the biochemical nature of fats, the outer surface is highly negatively charged and repellent. 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. Our cells have evolved to ward off such intrusions. 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. In the world of parasites, many bacterial or fungal pathogens can survive on their own without a host cell to infect. But what exactly is the spike protein and why is it so important? The SARS-CoV-2 coronavirus molecule. The spike protein is also the basis of current COVID-19 vaccines, which seek to generate an immune response against it. ![]() The new mutations may alter the biochemistry of the spike and could affect how transmissible the virus is. 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 emergence of a new variant of coronavirus has sparked renewed interest in the part of the virus known as the spike protein. ![]()
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