Structural and electrostatic determinants of RNA recognition by the CSFV Erns glycoprotein.

Classical swine fever virus (CSFV) employs the envelope glycoprotein Erns as a secreted viral ribonuclease that suppresses host innate immune recognition by degrading extracellular RNA. Despite extensive functional characterization, the structural determinants governing RNA recognition remain poorly defined because no high-resolution experimental structure is available. This study provides an integrative structural analysis of CSFV Erns combining evolutionary conservation mapping, electrostatic surface characterization, RNA docking, and intrinsic dynamics analysis to identify a conserved RNA-recognition interface. This approach reveals a structurally defined electropositive groove adjacent to the catalytic site that likely guides RNA substrate engagement during immune evasion. Structural modeling and validation indicate that the predicted Erns structure adopts a canonical RNase T2 fold with a highly conserved catalytic core. Conservation mapping across diverse CSFV isolates reveals strong evolutionary constraints extending beyond catalytic residues to adjacent surface-exposed regions. Electrostatic analysis identifies a conserved electropositive groove proximal to the RNase active site, consistent with a defined RNA-recognition surface. Docking consistently positions double-stranded RNA within this groove, while elastic network-based correlated motion analysis reveals coordinated collective movements associated with the predicted binding region. Interface profiling further identifies stabilizing hydrogen bonds and hydrophobic contacts at the Erns–RNA interface. Together, these complementary structure-based findings provide predictive mechanistic insight into Erns-mediated RNA recognition and immune evasion and establish a structural framework for future experimental validation of CSFV pathogenesis and for guiding biochemical and structural.