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Updated: Aug 12, 2026

Protein Misfolding Cyclic Amplification of Prions
Published on: November 7, 2012
Circular proteins--no end in sight
1Institute for Molecular Bioscience, University of Queensland, QLD 4072, Brisbane, Australia.
Abstract:
Circular proteins are a recently discovered phenomenon. They presumably evolved to confer advantages over ancestral linear proteins while maintaining the intrinsic biological functions of those proteins. In general, these advantages include a reduced sensitivity to proteolytic cleavage and enhanced stability. In one remarkable family of circular proteins, the cyclotides, the cyclic backbone is additionally braced by a knotted arrangement of disulfide bonds that confers additional stability and topological complexity upon the family. This article describes the discovery, structure, function and biosynthesis of the currently known circular proteins. The discovery of naturally occurring circular proteins in the past few years has been complemented by new chemical and biochemical methods to make synthetic circular proteins; these are also briefly described.
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