Recombinant protein of the receptor binding domain (RBD), Mutant (L452R-T478K) of SARS-CoV-2 (COVID-2019) Spike S1 from Wuhan pneumonia virus with N-terminal His-Tag and C-terminal GFP. The mutations L452R-T478K are characteristic for the fast spreading SARS-CoV-2 virus variants B.1.617 emerged in India. These mutations are affecting the receptor binding domain (RBD) of the spike protein, which the virus uses to bind to human cells receptors and enter them. Due to the mutations, the virus is allowed to bind with higher affinity to human ACE2 receptor which results in increased transmissibility of the SARS-CoV-2 virus.
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. A new SARS-CoV-2 lineage called B.1.617, exhibits 13 mutations. Compared to the previously circulating variants, the mutations L452R and T478K of the SARS-CoV-2 Spike S1 (RBD) may cause a stronger affinity of the spike protein to hACE2 and also conferring an increasing ability to evade the hosts’ immune system.