Low-Frequency ORF4b Variants in MERS-CoV Perturb PDE-Mediated IFN Antagonism at Catalytic H35/H37/H39, NLS K45, and Structural P95 Under Purifying Selection

This dataset presents a residue-resolution surveillance of MERS-CoV ORF4b, an accessory protein that suppresses type I interferon by degrading 2′-5′ oligoadenylates via its phosphodiesterase (PDE) activity. We specifically interrogate experimentally validated functional elements: Catalytic His-rich motif (H35, H37, H39, E38): essential for PDE enzymatic functionNuclear localization signal (NLS; residues 43 - 50): required for nuclear import and IRF3/7 antagonismRNase L interaction surface (residues 60 - 79): mediates substrate recognitionStructural proline P95: maintains loop conformation Across 587 global ORF4b sequences, all observed variants are low-frequency (