The spike (S) glycoprotein of coronaviruses is essential for binding of the virus to the host cell at the beginning of the infection process. The target protein is also a major immunogen and a possible target for entry inhibitors. The SARS-CoV-2 spike (S) protein is a large type I transmembrane protein composed of two subunits, S1 and S2. The S1 subunit contains a receptor-binding domain (RBD) responsible for binding to the host cell receptor angiotensin-converting enzyme 2 (ACE2). Several mutants of the spike protein are known. There is strong evidence that this particular mutation increases the infectivity of SARS-CoV-2 and the ability of the host to evade the immune system. Of all the amino acid changes in the Colombian Mu variant, the E484K mutation was previously discovered in the Alpha (UK), Beta (South Africa), and Gamma (Brazil) lineages, and is thought to further enhance the ability to evade the immune system. The N501Y mutation site in this variant leads to an enhancement of viral transmission. Early studies showed that this new variant has lower susceptibility to convalescent plasma. In addition, the Mu variant contains the R346K mutation, which has been detected in dominant circulating variants of the virus responsible for COVID-19 disease. The Mu variant is classified as a "variant of interest" (VOI) by the World Health Organization (WHO).
