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Related Concept Videos

Protein Organization01:13

Protein Organization

Overview
Protein Organization01:24

Protein Organization

Proteins are polymers of amino acid residues. They are versatile and responsible for different cellular functions, including DNA replication, molecular transport, catalysis, and structural support. Proteins have a hierarchical structure comprising at least three levels of organization: primary, secondary, and tertiary structure. Some large proteins have a quaternary structure where individual protein subunits are linked together.
The primary structure of a protein is its amino acid sequence.
Protein Folding01:25

Protein Folding

Proteins are chains of amino acids linked together by peptide bonds. Upon synthesis, a protein folds into a three-dimensional conformation, critical to its biological function. Interactions between its constituent amino acids guide protein folding, and hence the protein structure is primarily dependent on its amino acid sequence.
Protein Structure Is Critical to Its Biological Function
Proteins perform a wide range of biological functions such as catalyzing chemical reactions, providing...
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Protein and Protein Structure02:15

Protein and Protein Structure

Proteins are one of the most abundant organic molecules in living systems and have the most diverse range of functions of all macromolecules. Proteins may be structural, regulatory, contractile, or protective. They may serve in transport, storage, or membranes; or they may be toxins or enzymes. Their structures, like their functions, vary greatly. They are all, however, amino acid polymers arranged in a linear sequence.
A protein's shape is critical to its function. For example, an enzyme can...
Amino acids03:42

Amino acids

Amino acids are the monomers that comprise proteins. Each amino acid has the same fundamental structure, which consists of a central carbon atom, or the alpha (α) carbon, bonded to an amino group (NH2), a carboxyl group (COOH), and to a hydrogen atom. Every amino acid also has another atom or group of atoms bonded to the central atom known as the R group. There are 20 common amino acids present in proteins, each with a different R group. Variation in the amino acid sequence is responsible for...

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Positional effects on helical Ala-based peptides.

Richard P Cheng1, Prashant Girinath, Yuta Suzuki

  • 1Department of Chemistry, National Taiwan University, Taipei, Taiwan. rpcheng@ntu.edu.tw

Biochemistry
|October 8, 2010
PubMed
Summary
This summary is machine-generated.

Helix propensity, crucial for protein folding and foldamer design, is generally position-independent. However, this study found higher helix formation near the C-terminus, impacting helical peptide and protein design.

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Area of Science:

  • Biochemistry
  • Structural Biology
  • Peptide Chemistry

Background:

  • Helix-coil equilibrium studies are vital for understanding protein folding and designing helical foldamers.
  • Statistical mechanical models often assume position-independent helix propensity, an assumption needing experimental validation.

Purpose of the Study:

  • To investigate the position-dependence of helix propensity in Ala-based peptides.
  • To quantify helix propensities for Leucine (Leu), Phenylalanine (Phe), and Phenylalanine-like (Pff) residues at specific positions.

Main Methods:

  • Synthesized 19-residue Ala-based peptides with Leu, Phe, or Pff substitutions at positions 6, 11, and 16.
  • Utilized Circular Dichroism (CD) spectroscopy to measure the fraction of helix formation.
  • Derived helix propensities from CD data and surveyed protein structures.

Main Results:

  • Helix propensity followed the trend: position 16 (C-terminus) > position 6 > position 11.
  • Helix propensities for Leu, Phe, and Pff were similar at positions 6 and 11 but significantly higher at position 16.
  • Protein helix analysis revealed frequent Leu/Phe-Lys patterns near the C-terminus, with limited direct interactions observed.

Conclusions:

  • Helix propensity is generally position-independent, with notable exceptions near chain termini or in the presence of alternative structures.
  • The increased propensity at position 16 may be attributed to helix capping or 3₁₀-helix formation.
  • Findings will aid in the rational design of helical peptides, proteins, and foldamers.