English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

The dsRNA-activated protein kinase, PKR, plays a pivotal role in the cellular antiviral response. PKR contains an N-terminal dsRNA binding domain (dsRBD) and a C-terminal kinase domain. An autoinhibition model has been proposed in which latent PKR exists in a closed conformation where the substrate binding cleft of the kinase is blocked by the dsRBD. Binding to dsRNA activates the enzyme by inducing an open conformation and enhancing dimerization. We have tested this model by characterizing the affinity and kinetics of binding of a nucleotide substrate to PKR. The fluorescent nucleotide mant-AMPPNP binds to unactivated PKR with a Kd of approximately 30 microM, and the affinity is not strongly affected by autophosphorylation or binding to dsRNA. We observe biphasic binding kinetics in which the fast phase depends on ligand concentration but the slow phase is ligand-independent. The kinetic data fit to a two-step model of ligand binding followed by a slow conformation change. The kinetics are also not strongly affected by phosphorylation state or dsRNA binding. Thus, the equilibrium and kinetic data indicate that the substrate accessibility of the kinase is not modulated by PKR activation state as predicted by the autoinhibition model. In atomic force microscopy images, monomers of the latent protein are resolved with three separate regions linked by flexible, bridgelike structures. The resolution of the individual domains in the images supports a model in which unactivated PKR exists in an open conformation where the kinase domain is accessible and capable of binding substrate.

Unactivated PKR Exists in an Open Conformation Capable of Binding Nucleotides