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Related Concept Videos

Conservation of Protein Domains Over Different Proteins02:26

Conservation of Protein Domains Over Different Proteins

Protein domains are small structurally independent units that are part of a single amino acid chain.  Although these domains are often structurally independent, they may rely on synergistic effects to perform their functions as part of a larger protein. Protein domains may be conserved within the same organism, as well as across different organisms.
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Globular and Fibrous Proteins02:21

Globular and Fibrous Proteins

Many proteins can be classified into two distinct subtypes - globular or fibrous. These two types differ in their shapes and solubilities.
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Globular and Fibrous Proteins02:21

Globular and Fibrous Proteins

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Cytoskeletal Proteins in Bacteria01:29

Cytoskeletal Proteins in Bacteria

Bacterial cells were initially considered simple, randomly organized structures lacking a cytoskeleton. However, the discovery of cytoskeleton homologs in bacteria led to the change of this opinion. Bacterial cytoskeletal filaments regulate the cell shape, cell polarity, cell division, and partitioning of plasmids during cell division. It was later discovered that bacterial cytoskeletal proteins, mainly actin and tubulin homologs, are diverse compared to their eukaryotic counterparts. On the...
Porin Insertion in the Outer Mitochondrial Membrane01:12

Porin Insertion in the Outer Mitochondrial Membrane

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Bacterial RNA Polymerase00:43

Bacterial RNA Polymerase

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Updated: Jun 8, 2026

In Silico Identification and Characterization of circRNAs During Host-Pathogen Interactions
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In Silico Identification and Characterization of circRNAs During Host-Pathogen Interactions

Published on: October 21, 2022

Naturally occurring circular proteins: distribution, biosynthesis and evolution.

Laura Cascales1, David J Craik

  • 1The University of Queensland, Institute for Molecular Bioscience, Brisbane, QLD 4072, Australia.

Organic & Biomolecular Chemistry
|September 14, 2010
PubMed
Summary
This summary is machine-generated.

Circular proteins, featuring a continuous amino acid circle, are stable defense molecules found across diverse organisms. Further research is needed to uncover more cyclic peptides and their potential in drug design.

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Area of Science:

  • Biochemistry
  • Molecular Biology
  • Structural Biology

Background:

  • Circular proteins possess a unique backbone structure formed by a continuous, seamless circle of amino acids.
  • These proteins are exceptionally stable and function as defense mechanisms in various organisms, including bacteria, plants, fungi, and animals.
  • Cyclotides represent the largest known family of circular proteins, primarily found in plants and involved in defense against insect predation.

Purpose of the Study:

  • To review and describe the known families of ribosomally synthesized cyclic proteins.
  • To examine the common features, distribution, biosynthesis, and evolution of circular proteins.
  • To highlight the potential of circular proteins as scaffolds for drug design due to their inherent stability.

Main Methods:

  • Literature review of reported ribosomally synthesized cyclic proteins.
  • Analysis of common structural and functional features.
  • Examination of distribution, biosynthesis, and evolutionary aspects.

Main Results:

  • Circular proteins are found in diverse taxa and exhibit remarkable stability.
  • Cyclotides are a prominent family, particularly in plants, serving defensive roles.
  • Evidence suggests cyclic peptides are an underdiscovered class with potential for future findings.

Conclusions:

  • Circular proteins' unique structure confers high stability, making them valuable for drug design.
  • Re-engineering linear proteins into circular structures is a viable strategy for enhanced stability.
  • The study underscores the significance of circular proteins and advocates for further exploration of this molecular class.