Cobalt(III)-Schiff Base Coordination to Nsp1, a SARS-CoV-2 Protein

Area of Science:

• Biochemistry
• Virology
• Inorganic Chemistry

Background:

• Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nonstructural protein 1 (Nsp1) inhibits host immune defenses by blocking mRNA translation.
• Nsp1 obstructs the 40S ribosomal subunit's mRNA entry channel, a critical step in viral immune evasion.
• Understanding Nsp1 inhibition mechanisms is vital for developing antiviral strategies.

Purpose of the Study:

• To investigate if the cobalt complex Co(III)(acacen)(NH3)2+ can disrupt SARS-CoV-2 Nsp1 function.
• To explore the potential of targeting Nsp1's histidine residues with a cobalt complex.
• To assess the impact of Co(III)(acacen)(NH3)2+ on Nsp1-mediated inhibition of host protein synthesis.

Main Methods:

• 59Co nuclear magnetic resonance (NMR) spectroscopy to study the interaction between Co(III)(acacen)(NH3)2+ and an Nsp1 peptide.
• Computational analysis to model the coordination structure of the cobalt complex with histidine residues.
• Proteolytic fragmentation and mass spectrometry to identify Nsp1 histidine binding sites.
• In vitro translation assays to evaluate the effect of the cobalt complex on host protein synthesis.

Main Results:

• Co(III)(acacen)(NH3)2+ undergoes axial ligand substitution, with an NH3 ligand displaced by a histidine imidazole from an Nsp1 peptide.
• Computational analysis confirmed coordination involving histidine imidazole displacement.
• Mass spectrometry identified multiple histidine binding sites (His13, His81/His83 region, His165) on full-length Nsp1.
• In vitro translation assays showed that Co(III)(acacen)(NH3)2+ did not restore host protein synthesis.

Conclusions:

• Co(III)(acacen)(NH3)2+ interacts with SARS-CoV-2 Nsp1, specifically coordinating to histidine residues.
• Despite binding, the cobalt complex failed to restore host protein synthesis inhibited by Nsp1.
• Further research is needed to develop effective Nsp1 inhibitors for antiviral therapies.