Molecular and Structural Characterisation of the MERS-Coronavirus Polymerase

The minimal MERS-CoV replication-transcription complex is structurally similar to the SARS-CoV-2 RTC and is inhibited by suramin, enabling cross-species polymerase-cofactor compatibility mapping.

• Why it matters: MERS-CoV has a 36.5% case fatality rate and no approved treatments, while limited RTC structural and biochemical data constrain antiviral design.
• What they did: Using in vitro and single-molecule assays, the authors tested suramin susceptibility and solved a structure of the minimal MERS-CoV RTC bound to an RNA duplex. Cross-subunit swapping assessed whether MERS-CoV NSP12 uses SARS-CoV-2 NSP7/NSP8 and whether SARS-CoV-2 NSP12 works with MERS-CoV NSP8.
• The result: The minimal MERS-CoV RTC is susceptible to suramin and shows strong structural similarity to the SARS-CoV-2 RTC; swapping reveals efficient MERS-CoV NSP12 use of SARS-CoV-2 cofactors but reduced SARS-CoV-2 NSP12 activity with MERS-CoV NSP8. This provides a structural-mechanistic framework for MERS-CoV RNA synthesis and supports conserved RTC targeting for broadly acting coronavirus antivirals.

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