Molecular Mechanism for Inhibition of G Protein-Coupled Receptor Kinase 2 by a Selective RNA Aptamer

SummaryCardiovascular homeostasis is maintained in part by the rapid desensitization of activated heptahelical receptors that have been phosphorylated by G protein-coupled receptor kinase 2 (GRK2). However, during chronic heart failure GRK2 is upregulated and believed to contribute to disease progression. We have determined crystallographic structures of GRK2 bound to an RNA aptamer that potently and selectively inhibits kinase activity. Key to the mechanism of inhibition is the positioning of an adenine nucleotide into the ATP-binding pocket and interactions with the basic αF-αG loop region of the GRK2 kinase domain. Constraints imposed on the RNA by the terminal stem of the aptamer also play a role. These results highlight how a high-affinity aptamer can be used to selectively trap a novel conformational state of a protein kinase.

Graphical AbstractFigure optionsDownload high-quality image (621 K)Download as PowerPoint slideHighlights
► C13 RNA aptamer variants stabilize GRK2 in a unique and remodeled conformation
► The aptamer positions an adenine nucleotide into the ATP-binding pocket of GRK2
► Basic residues on an exterior surface of GRK2 facilitate aptamer binding
► The terminal stem of the aptamer indirectly contributes to affinity