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G-actin provides substrate-specificity to eukaryotic initiation factor 2α holophosphatases

DOI: 10.7554/eLife.04871 DOI Help
PMID: 25774600 PMID Help

Authors: Ruming Chen (University of Cambridge) , Cláudia Rato (University of Cambridge) , Yahui Yan (University of Cambridge) , Ana Crespillo-casado (University of Cambridge) , Hanna J Clarke (University of Cambridge) , Heather P Harding (University of Cambridge) , Stefan J Marciniak (University of Cambridge) , Randy Read (University of Cambridge) , David Ron (University of Cambridge)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Elife , VOL 4

State: Published (Approved)
Published: March 2015
Diamond Proposal Number(s): 8547

Open Access Open Access

Abstract: Dephosphorylation of eukaryotic translation initiation factor 2a (eIF2a) restores protein synthesis at the waning of stress responses and requires a PP1 catalytic subunit and a regulatory subunit, PPP1R15A/GADD34 or PPP1R15B/CReP. Surprisingly, PPP1R15-PP1 binary complexes reconstituted in vitro lacked substrate selectivity. However, selectivity was restored by crude cell lysate or purified G-actin, which joined PPP1R15-PP1 to form a stable ternary complex. In crystal structures of the non-selective PPP1R15B-PP1G complex, the functional core of PPP1R15 made multiple surface contacts with PP1G, but at a distance from the active site, whereas in the substrate-selective ternary complex, actin contributes to one face of a platform encompassing the active site. Computational docking of the N-terminal lobe of eIF2a at this platform placed phosphorylated serine 51 near the active site. Mutagenesis of predicted surface-contacting residues enfeebled dephosphorylation, suggesting that avidity for the substrate plays an important role in imparting specificity on the PPP1R15B-PP1G-actin ternary complex.

Subject Areas: Biology and Bio-materials


Beamlines: I02-Macromolecular Crystallography , I03-Macromolecular Crystallography , I04-1-Macromolecular Crystallography (fixed wavelength)