Lybatides from Lycium barbarum Contain An Unusual Cystine-stapled Helical Peptide Scaffold

Wei Liang Tan,James P Tam,Ka H Wong,Rolf Hilgenfeld,Naoki Sakai,Jian Lei,Hong Wei Tan

doi:10.1038/s41598-017-05037-1

Abstract

Cysteine-rich peptides (CRPs) of 2–6 kDa are generally thermally and proteolytically stable because of their multiple cross-bracing disulfide bonds. Here, we report the discovery and characterization of two novel cystine-stapled CRPs, designated lybatide 1 and 2 (lyba1 and lyba2), from the cortex of Lycium barbarum root. Lybatides, 32 to 33 amino acids in length, are hyperstable and display a novel disulfide connectivity with a cysteine motif of C-C-C-C-CC-CC which contains two pairs of adjacent cysteines (-CC-CC). X-ray structure analysis revealed the presence of a single cystine-stabilized (α + π)-helix in lyba2, a rare feature of CRPs. Together, our results suggest that lybatides, one of the smallest four-disulfide-constrained plant CRPs, is a new family of CRPs. Additionally, this study provides new insights into the molecular diversity of plant cysteine-rich peptides and the unusual lybatide scaffold could be developed as a useful template for peptide engineering and therapeutic development.

Highlights

DiGuPi in Chinese) is commonly used as a traditional Chinese medicine for treating chronic low-grade fever, cough, hemoptysis and hematuria, diabetes mellitus and hypertension[1]
Mass spectrometry-guided screening of an aqueous extract of L. barbarum root bark revealed the presence of two peptides with m/z 3509 and 3616 Da (Fig. 2A)
Alignment of lybatides revealed that they contain eight highly conserved cysteine residues arranged in a unique spacing of C-C-C-C-CC-CC, with a sequence identity of 76.5% between the two

Summary

Introduction

DiGuPi in Chinese) is commonly used as a traditional Chinese medicine for treating chronic low-grade fever, cough, hemoptysis and hematuria, diabetes mellitus and hypertension[1]. Even in studies relating to identifying peptides from plants, the focus is largely on small cyclic peptides This bias is attributed to a general perception that peptides >2 kDa are unstable and readily denatured during a decoction preparation or in the gastrointestinal tract after ingestion. This is generally true for large peptides and proteins with molecular weight >8 kDa. cysteine-rich peptides (CRPs) with a molecular range of. Plant CRPs within the chemical space of 2–6 kDa can be arbitrarily classified into two major groups (Fig. 1). They are the cystine-stabilized α-helical (CSα) peptides and cystine-stabilized β-peptides

Results

Discussion

Conclusion