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  • A substrate-driven allosteric switch that enhances PDI catalytic activity.

A substrate-driven allosteric switch that enhances PDI catalytic activity.

Nature communications (2016-08-31)
Roelof H Bekendam, Pavan K Bendapudi, Lin Lin, Partha P Nag, Jun Pu, Daniel R Kennedy, Alexandra Feldenzer, Joyce Chiu, Kristina M Cook, Bruce Furie, Mingdong Huang, Philip J Hogg, Robert Flaumenhaft
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.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Bepristat 2a hydrochloride, ≥95% (HPLC)
Sigma-Aldrich
Bepristat 1a, ≥98% (HPLC)