α 1 -Antitrypsin Portland, a bioengineered serpin highly selective for furin: Application as an antipathogenic agent

Authors:
Publisher website
Google Scholar
Abstract
The important role of furin in the proteolytic activation of many pathogenic molecules has made this endoprotease a target for the development of potent and selective antiproteolytic agents. Here, we demonstrate the utility of the protein-based inhibitor α 1 -antitrypsin Portland (α 1 -PDX) as an antipathogenic agent that can be used prophylactically to block furin-dependent cell killing by Pseudomonas exotoxin A. Biochemical analysis of the specificity of a bacterially expressed His- and FLAG-tagged α 1 -PDX (α 1 -PDX/hf) revealed the selectivity of the α 1 -PDX/hf reactive site loop for furin ( K i , 600 pM) but not for other proprotein convertase family members or other unrelated endoproteases. Kinetic studies show that α 1 -PDX/hf inhibits furin by a slow tight-binding mechanism characteristic of serpin molecules and functions as a suicide substrate inhibitor. Once bound to furin’s active site, α 1 -PDX/hf partitions with equal probability to undergo proteolysis by furin at the C-terminal side of the reactive center -Arg 355 -Ile-Pro-Arg 358 - ↓ or to form a kinetically trapped SDS-stable complex with the enzyme. This partitioning between the complex-forming and proteolytic pathways contributes to the ability of α 1 -PDX/hf to differentially inhibit members of the proprotein convertase family. Finally, we propose a structural model of the α 1 -PDX-reactive site loop that explains the high degree of enzyme selectivity of this serpin and which can be used to generate small molecule furin inhibitors.

This publication has 34 references indexed in Scilit: