Structural Modeling Identifies a Conserved ADAR1 dsRBDIII Motif Predicted to Interact with PKR at Thr451

Abstract

Protein kinase R (PKR) is a key cellular dsRNA sensor whose activation is regulated by ADAR1. Although ADAR1 PKR association is established, its molecular determinants remain poorly understood. Molecular docking identified a conserved W768/F769/P770 (WFP) motif within ADAR1 dsRBD III as a potential PKR interaction interface. Disruption of this motif altered the predicted binding configuration. However, coimmunoprecipitation revealed no significant reduction in PKR association following individual substitutions or deletion of the WFP motif, although the deletion showed a consistent trend toward reduced binding. RNase treatment reduced PKR coimmunoprecipitation approximately tenfold without abolishing the interaction. These findings suggest that ADAR1 PKR association is predominantly RNA dependent, potentially involving shared dsRNA substrates that facilitate direct protein protein contacts, with the WFP motif contributing to interaction stability.