Singular Interface Dynamics of the SARS-CoV-2 Delta Variant Explained with Contact Perturbation Analysis.

Area of Science:

• Virology and Molecular Biology
• Structural Biology
• Computational Biology

Background:

• Emerging SARS-CoV-2 variants pose significant challenges to global COVID-19 pandemic control.
• Understanding the mechanistic differences of viral variants, particularly their spike protein interactions, is crucial for developing effective countermeasures.

Purpose of the Study:

• To investigate the structural and dynamic differences between the SARS-CoV-2 wild type and five emergent variants (Alpha, Beta, Gamma, Delta, Epsilon).
• To focus on the spike protein's interaction with the human angiotensin-converting enzyme 2 (ACE2) receptor and elucidate the molecular mechanisms driving variant dominance.

Main Methods:

• Utilized crystallographic structures of the SARS-CoV-2 spike protein and ACE2 receptor.
• Performed microsecond molecular dynamics simulations to analyze protein dynamics.
• Applied dihedral angle principal component analysis (PCA) and dynamical perturbation networks to characterize interface dynamics.

Main Results:

• Spike receptor binding domain (RBD) dynamics were similar across Alpha, Beta, Gamma, and Delta variants, differing from wild type (WT) and Epsilon.
• The Delta variant exhibited unique interface dynamics not directly explained by its L452R and T478K mutations alone, as these residues do not directly contact ACE2.
• Synergistic effects of Delta's L452R and T478K mutations on neighboring residues were identified, causing significant alterations in the spike/ACE2 interface.

Conclusions:

• The Delta variant's dominance is attributed to a unique mechanism where specific mutations indirectly induce substantial changes in the spike-ACE2 interface dynamics.
• This study highlights the complex interplay of mutations and their impact on viral-host interactions, crucial for understanding variant evolution and spread.