Structure and Activity of the Leaf-Specific Cyclotide vhl-2

Norelle L. Daly; Bin Chen; Philip Nguyencong; David J. Craik

doi:10.1071/CH10007

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Structure and Activity of the Leaf-Specific Cyclotide vhl-2

Norelle L. Daly ^A , Bin Chen ^A ^B ^C , Philip Nguyencong ^A and David J. Craik ^A ^D

+ Author Affiliations

- Author Affiliations

^A The University of Queensland, Institute for Molecular Bioscience, Division of Chemistry and Structural Biology, Brisbane, Qld 4072, Australia.

^B Centre for Natural Products, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, China.

^C Present address: Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742, USA.

^D Corresponding author. Email: d.craik@imb.uq.edu.au

Australian Journal of Chemistry 63(5) 771-778 https://doi.org/10.1071/CH10007
Submitted: 4 January 2010 Accepted: 18 March 2010 Published: 21 May 2010

Abstract

Cyclotides are plant-derived macrocyclic peptides with potential applications in the pharmaceutical and agricultural industries. In addition to their presumed natural function as host-defence peptides arising from their insecticidal activity, their other biological activities include antimicrobial, haemolytic, and cytotoxic activities, but at present, only limited information is available on the structural and chemical features that are important for these various activities. In the current study, we determined the three-dimensional structure of vhl-2, a leaf-specific cyclotide. Although the characteristic cyclic cystine knot fold of other cyclotides is maintained in vhl-2, it has more potent haemolytic activity than well-characterized cyclotides such as kalata B1 and kalata B8. Analysis of surface hydrophobicity and haemolytic activity for a range of cyclotides indicates a correlation between them, with increasing hydrophobicity resulting in increased haemolytic activity. This correlation is consistent with membrane binding being a vital step in mediating the various cytotoxic activities of cyclotides. The gene sequence for vhl-2 was determined and indicates that vhl-2 is processed from a multidomain precursor protein that also encodes the cyclotide cycloviolacin H3.

Acknowledgements

This work was supported by a grant from the Australian Research Council (ARC). D.J.C. is a National Health and Medical Research Council Principal Research Fellow. B.C. acknowledges financial support from the National Natural Science Foundation of China (grant no. 20772121). N.L.D. is a Queensland Smart State Fellow. The primer targeting the AAFALPA sequence in the ER signal of cyclotide clones was designed and supplied by Lillian Sando. The analytical HPLC traces were collected by Richard Clark and we thank Michelle Colgrave for her assistance with the haemolytic assay and Rekha Bharathi for purifying the peptides that were used in this analysis.

References

Structure and Activity of the Leaf-Specific Cyclotide vhl-2

Abstract

Acknowledgements

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