Structure of Omicron variant explains evasion of antibodies and how mutations affect receptor binding
First reported last November in South Africa, the Omicron variant of SARS-CoV-2, the virus responsible for COVID-19, has since rapidly spread around the world. Key to understanding Omicron’s success is the spike protein, which allows SARS-CoV-2 to penetrate human cells by latching onto a cell surface protein, angiotensin-converting enzyme 2 (ACE2). Compared to the original strain of SARS-CoV-2, Omicron’s spike protein displays 37 mutations, including 15 in its receptor-binding domain, the section that connects with ACE2. Cryogenic electron microscopy reveals how these changes affect the spike protein’s structure (pictured, in purple), and its interactions with ACE2 (in turquoise). Despite its many changes, Omicron’s spike protein strongly binds ACE2, with a similar efficiency to the spike protein of the Delta variant. Conversely, antibodies from patients both vaccinated or recovered from infections with other variants were less successful in neutralising Omicron’s spike protein, suggesting its mutations help it evade the immune response.
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