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Structural Prediction of Coronavirus s2m Kissing Complexes and Extended Duplexes

Kensinger AH, Makowski JA, Mihailescu MR, Evanseck JD

ACS physical chemistry Au, 2025

Abstract

The three-dimensional (3D) atomistic-resolution structure and dynamics of RNA kissing complexes (KCs) and extended duplexes (EDs), homodimers formed through palindromic base pairing, are crucial for understanding viral replication and structure-informed therapeutic design. Polyacrylamide gel electrophoresis (PAGE) evidence suggests KC and ED dimer formation between stem-loop II motif (s2m) elements in SARS-CoV, SARS-CoV-2, and Delta SARS-CoV-2, which may regulate host immune response. However, the absence of 3D structural data on s2m dimers limits structural interpretation needed to explain differences in stability indicated by native PAGE and biophysical implications. In this work, we evaluate the VFold3D/LA-IsRNA pipeline for resolving 3D structures of s2m KCs and EDs by validating its accuracy with blind and referenced predictions against experimental HIV-1 DIS KC and ED structures. Engendering confidence in the approach for blind prediction of KC and ED structures, HIV-1 DIS predictions achieved an average RMSD of 3.28 Å relative to crystal structures, while local interactions, such as palindrome-flanking purine stack orientations in the terminal loops, were in closer agreement with reported solution-phase NMR (RMSD ∼ 2.5 Å), cryo-EM maps, and previous molecular dynamics (MD) simulations. We find that the predicted 3D dimer structures of s2m resulted in kinked or linear shapes of s2m KC complexes that provide an interpretation consistent with native PAGE migration…

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