Engineering stable peptide toxins by means of backbone cyclization: Stabilization of the α-conotoxin MII

doi:10.1073/pnas.0504613102

Engineering stable peptide toxins by means of backbone cyclization: Stabilization of the α-conotoxin MII

^*Institute for Molecular Bioscience and ^†School of Biomedical Sciences, University of Queensland, Brisbane QLD 4072, Australia

Edited by Alexander M. Klibanov, Massachusetts Institute of Technology, Cambridge, MA, and approved July 26, 2005 (received for review June 6, 2005)

Abstract

Conotoxins (CTXs), with their exquisite specificity and potency, have recently created much excitement as drug leads. However, like most peptides, their beneficial activities may potentially be undermined by susceptibility to proteolysis in vivo. By cyclizing the α-CTX MII by using a range of linkers, we have engineered peptides that preserve their full activity but have greatly improved resistance to proteolytic degradation. The cyclic MII analogue containing a seven-residue linker joining the N and C termini was as active and selective as the native peptide for native and recombinant neuronal nicotinic acetylcholine receptor subtypes present in bovine chromaffin cells and expressed in Xenopus oocytes, respectively. Furthermore, its resistance to proteolysis against a specific protease and in human plasma was significantly improved. More generally, to our knowledge, this report is the first on the cyclization of disulfide-rich toxins. Cyclization strategies represent an approach for stabilizing bioactive peptides while keeping their full potencies and should boost applications of peptide-based drugs in human medicine.

Footnotes

↵ ‡ To whom correspondence should be addressed. E-mail: d.craik{at}imb.uq.edu.au.
Author contributions: R.J.C., N.L.D., F.A.M., D.J.A., and D.J.C. designed research; R.J.C., H.F., L.D., K.J.R., and S.T.N. performed research; R.J.C., H.F., L.D., K.J.R., and S.T.N. analyzed data; and R.J.C., H.F., N.L.D., F.A.M., D.J.A., and D.J.C. wrote the paper.
This paper was submitted directly (Track II) to the PNAS office.
Abbreviations: CTX, conotoxin; nAChR, nicotinic acetylcholine receptor; NOE, nuclear Overhauser effect.
Data deposition: The atomic coordinates and structure factors have been deposited in the Protein Data Bank, www.pdb.org [PDB ID codes 2AJW (cMII-6) and 2AK0 (cMII-7)].