Secondary Structure as a Conformational Determinant in Processing of Peptide Precursors at Dibasic Amino Acids

Noureddine Lazar,Paul Cohen,Noureddine Brakch,Mohamed Rholam,Maï Panchal

doi:10.1155/2003/819640

Abstract

The aim of this work was to establish the functional role of selected secondary structure motifs of peptide hormone precursors in their selective recognition by the corresponding converting endoproteases. The strategy was based on the use of synthetic peptides either reproducing or mimicking the sequences of the cleavage regions of two distinct models; i.e. pro-ocytocin–neurophysin and prosomatostatin. Both prohormones were capable to release their biologically active sequences either by cleavage at a dibasic stretch or by proteolysis at a monobasic site.Both kinetic and thermodynamic parameters of peptide cleavage by various convertases were measured. They were examined in light of structural data on preferred conformations adopted by these substrates, which were obtained by a combination of spectroscopical techniques including CD, FT-IR and proton NMR. In the case of prosomatostatin, these approaches were in addition paralleled by site-directed mutagenesis experiments.The wealth of collected data point toward the conclusion thatβ-turns and/or loops, favored by sequences bearing basic residues, constitute a key feature in the specification of those peptide loci which are proteolytically processedin vivo. They will be discussed with respect of other processing mechanisms where these mechanisms were also shown.

Highlights

Proteolytic processing is an important regulatory mechanism used by cells to control gene expression at the post-translational level
Peptide hormones and peptide transmitters are generated from polypeptide precursors by specific cleavage reactions which take place principally at sites formed by single or paired basic residues [6,7,8,9]
Not all the possible cleavage sites are utilised [6,7], and the degree of processing of many propeptides has been found to vary according to the tissue of origin [1,2,3,4,5]

Summary

Introduction

Proteolytic processing is an important regulatory mechanism used by cells to control gene expression at the post-translational level. Peptide hormones and peptide transmitters are generated from polypeptide precursors by specific cleavage reactions which take place principally at sites formed by single or paired basic residues [6,7,8,9]. Not all the possible cleavage sites are utilised [6,7], and the degree of processing of many propeptides has been found to vary according to the tissue of origin [1,2,3,4,5]. The restricted nature of processing reactions could point to the existence of a series of enzymes with stringent specificities [2,4,6], recognising regions of structure in addition to the single or paired basic residues. The action of processing enzymes may be directed by conformation of the pro-peptide which could focus the action of a protease onto or away from a particular site [2,7]

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Conclusion