Structural Characterization of the Loop at the Alpha-Subunit C-Terminus of the Mixed Lineage Leukemia Protein Activating Protease Taspase1.

Johannes Van Den Boom,Peter Bayer,Franziska Trusch,Lukas Hoppstock,Christine Beuck

doi:10.1371/journal.pone.0151431

Johannes Van Den Boom, Peter Bayer + Show 3 more

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https://doi.org/10.1371/journal.pone.0151431

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Journal: PloS one	Publication Date: Mar 14, 2016
Citations: 8	License type: CC BY 4.0

Affiliation: University of Duisburg-Essen, University of Aberdeen

Abstract

Type 2 asparaginases, a subfamily of N-terminal nucleophile (Ntn) hydrolases, are activated by limited proteolysis. This activation yields a heterodimer and a loop region at the C-terminus of the α-subunit is released. Since this region is unresolved in all type 2 asparaginase crystal structures but is close to the active site residues, we explored this loop region in six members of the type 2 asparaginase family using homology modeling. As the loop model for the childhood cancer-relevant protease Taspase1 differed from the other members, Taspase1 activation as well as the conformation and dynamics of the 56 amino acids loop were investigated by CD and NMR spectroscopy. We propose a helix-turn-helix motif, which can be exploited as novel anticancer target to inhibit Taspase1 proteolytic activity.

Highlights

Proteolysis is a common regulatory process governing several essential pathways such as apoptosis [1] or blood clotting [2]
This type of regulation is common for proteases, but is found among N-terminal nucleophile (Ntn) hydrolases involved in diverse cellular processes
Taspase1 differs from other type 2 asparaginase family proteins in that its substrates are polypeptide bonds instead of the modification of single amino acids and that it does not cleave itself only and acts as a protease in trans [6]

Summary

Introduction

Proteolysis is a common regulatory process governing several essential pathways such as apoptosis [1] or blood clotting [2]. In contrast to protein digestion and degradation, proteolytic activation events occur in a site-specific manner and induce a conformational change that increases the catalytic activity significantly [3]. This type of regulation is common for proteases, but is found among N-terminal nucleophile (Ntn) hydrolases involved in diverse cellular processes. Ntn hydrolases are typically activated from an enzymatically inactive zymogen by hydrolysis of the peptide bond N-terminal of the active site residue. Diverse substrate specificity and functions, all Ntn hydrolases share a common αββα-asparaginase fold

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