AaeAP1 and AaeAP2: novel antimicrobial peptides from the venom of the scorpion, Androctonus aeneas: structural characterisation, molecular cloning of biosynthetic precursor-encoding cDNAs and engineering of analogues with enhanced antimicrobial and anticancer activities.

Qiang Du,Jinao Duan,Mei Zhou,Chris Shaw,Hui Wang,Tianbao Chen,Xinping Xi,Minjie Wei,Yingqi Zhang,Xiaojuan Hou,Lei Wang

doi:10.3390/toxins7020219

Abstract

The main functions of the abundant polypeptide toxins present in scorpion venoms are the debilitation of arthropod prey or defence against predators. These effects are achieved mainly through the blocking of an array of ion channel types within the membranes of excitable cells. However, while these ion channel-blocking toxins are tightly-folded by multiple disulphide bridges between cysteine residues, there are additional groups of peptides in the venoms that are devoid of cysteine residues. These non-disulphide bridged peptides are the subject of much research interest, and among these are peptides that exhibit antimicrobial activity. Here, we describe two novel non-disulphide-bridged antimicrobial peptides that are present in the venom of the North African scorpion, Androctonus aeneas. The cDNAs encoding the biosynthetic precursors of both peptides were cloned from a venom-derived cDNA library using 3'- and 5'-RACE strategies. Both translated precursors contained open-reading frames of 74 amino acid residues, each encoding one copy of a putative novel nonadecapeptide, whose primary structures were FLFSLIPSVIAGLVSAIRN and FLFSLIPSAIAGLVSAIRN, respectively. Both peptides were C-terminally amidated. Synthetic versions of each natural peptide displayed broad-spectrum antimicrobial activities, but were devoid of antiproliferative activity against human cancer cell lines. However, synthetic analogues of each peptide, engineered for enhanced cationicity and amphipathicity, exhibited increases in antimicrobial potency and acquired antiproliferative activity against a range of human cancer cell lines. These data clearly illustrate the potential that natural peptide templates provide towards the design of synthetic analogues for therapeutic exploitation.

Highlights

The vast majority of scorpion venom toxins studied far function through altering the functions of cell membrane ion channels [1,2,3,4]
Screening of the reverse-phase HPLC fractions of lyophilised Androctonus aeneas venom for antimicrobial activity resulted in the identification of significant antimicrobial activity in a single fraction, number 145 (Figure 1)
Two novel antimicrobial peptides (AMPs)-encoding cDNAs were consistently amplified and cloned from the cDNA library derived from the venom of the scorpion, Androctonus aeneas, and each encoded a single copy of their respective mature peptides (Figure 2)

Summary

Introduction

The vast majority of scorpion venom toxins studied far function through altering the functions of cell membrane ion channels [1,2,3,4]. The classification schemes for scorpion toxins are various and depend on the criteria that are used They can be classified according to their molecular size (or, rather, their number of constituent amino acid residues) into long and short chain toxins or according to their mechanism of action into neurotoxic and cytotoxic toxins [1,2,3,4]. Another method used to classify scorpion toxins is based on the presence or absence of discrete structural features—disulphide bridges—and the two groups are those that have these and those that do not [7]. The ion channel-interacting toxins universally fall into the first group

Results

Discussion

Conclusion