A substrate-driven allosteric switch that enhances PDI catalytic activity

  • Nat Commun. 2016 Aug 30:7:12579. doi: 10.1038/ncomms12579.
Roelof H Bekendam  1 ,  Pavan K Bendapudi  1 ,  Lin Lin  1 ,  Partha P Nag  2  3 ,  Jun Pu  2 ,  Daniel R Kennedy  4 ,  Alexandra Feldenzer  4 ,  Joyce Chiu  5  6 ,  Kristina M Cook  5 ,  Bruce Furie  1 ,  Mingdong Huang  1 ,  Philip J Hogg  5  6 ,  Robert Flaumenhaft  1
Affiliations
  • 1. Division of Hemostasis and Thrombosis, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02115, USA.
  • 2. Department of Pharmaceutical and Administrative Sciences, The Broad Institute Probe Development Center, Cambridge, Massachusetts 02142, USA.
  • 3. Center for the Science of Therapeutics, Broad Institute, Cambridge, Massachusetts 02142, USA.
  • 4. College of Pharmacy, Western New England University, Springfield, Massachusetts 01119, USA.
  • 5. The Centenary Institute, Newtown, Sydney, New South Wales 2050, Australia.
  • 6. National Health and Medical Research Council Clinical Trials Centre, University of Sydney, Sydney, New South Wales 2050, Australia.
PMID: 27573496 DOI: 10.1038/ncomms12579
Abstract

Protein disulfide isomerase (PDI) is an oxidoreductase essential for folding proteins in the endoplasmic reticulum. The domain structure of PDI is a-b-b'-x-a', wherein the thioredoxin-like a and a' domains mediate disulfide bond shuffling and b and b' domains are substrate binding. The b' and a' domains are connected via the x-linker, a 19-amino-acid flexible peptide. Here we identify a class of compounds, termed bepristats, that target the substrate-binding pocket of b'. Bepristats reversibly block substrate binding and inhibit platelet aggregation and thrombus formation in vivo. Ligation of the substrate-binding pocket by bepristats paradoxically enhances catalytic activity of a and a' by displacing the x-linker, which acts as an allosteric switch to augment reductase activity in the catalytic domains. This substrate-driven allosteric switch is also activated by peptides and proteins and is present in Other thiol isomerases. Our results demonstrate a mechanism whereby binding of a substrate to thiol isomerases enhances catalytic activity of remote domains.

Products