SARS-CoV-2 Delta variant spike protein (Delta S)

The SARS-CoV-2 Delta variant spike protein is a trimeric glycoprotein on the viral envelope that mediates host cell entry by binding the ACE2 receptor via its receptor-binding domain (RBD) in the S1 subunit and driving membrane fusion through conformational changes in the S2 subunit. Key mutations like T478K and L452R in the RBD enhance ACE2 affinity at low receptor densities, while P681R near the furin cleavage site improves S1/S2 processing, enabling faster infection kinetics and higher transmissibility compared to earlier variants. The protein forms stable prefusion trimers but uniquely aggregates in pseudoparticles, potentially aiding collective infection, and shows N-terminal domain rearrangements that evade NTD-targeting antibodies. In COVID-19, it contributes to rapid viral replication, higher nasal loads, and breakthrough infections despite vaccination, though severe disease protection remains robust. Therapeutic antibodies like bamlanivimab lose potency due to RBD changes, prompting variant-specific boosters and broad-spectrum approaches. Cryo-EM structures reveal optimized RBD dynamics and glycan shielding that balance receptor engagement with immune escape.

Other names

B.1.617.2 spike proteinDelta spike glycoproteinDelta variant S protein

Neutralizing antibody binding to RBD or NTD (impaired by mutations), Vaccine-induced antibody blockade of ACE2-RBD interaction, Spike trimer stabilization to prevent conformational change for fusion