Protein Structure and Stability

Study Notes

Protein Structure and Stability

Protein structures are stabilized by noncovalent interactions and forces, including the hydrophobic effect, hydrogen bonds, ionic interactions, and van der Waals forces.

Secondary Structure

Protein segments can adopt regular secondary structures such as the α helix and the β conformation, which are defined by particular values of dihedral angles φ and ψ.
The formation of these structures is impacted by the amino acid composition of the segment.

Tertiary Structure

Tertiary structure describes the well-defined, three-dimensional fold adopted by a protein.
Protein structures are often built by combinatorial use of common protein folds or motifs.

Quaternary Structure

Quaternary structure describes the interactions between components of a multisubunit assembly.

Relationship Between Protein Structure and Function

The three-dimensional structures of proteins can be defined.
Structural biologists use a variety of instruments and computational methods to solve biomolecular structures.
Protein function relates to unique three-dimensional structures.

Conformations and Stability

Proteins can assume an uncountable number of special arrangements, or conformations, but only a limited number of conformations predominate under biological conditions.
Conformations are thermodynamically the most stable, with the lowest free energy (G).
Unfolded proteins have high conformational entropy, and chemical interactions stabilize native conformations.

Weak Interactions and Forces

Protein conformations are stabilized largely by weak interactions, including hydrogen bonds, the hydrophobic effect, and ionic interactions.
The hydrophobic effect is the predominating weak interaction, causing nonpolar groups to cluster together and decrease the solvation layer.
Hydrogen bonds and ion pairs contribute to protein folding, with repeating secondary structures optimizing hydrogen bonding and ion pair interactions.

Description

Learn about the noncovalent interactions and forces that stabilize protein structures, including the hydrophobic effect, hydrogen bonds, ionic interactions, and van der Waals forces. Understand how peptide bonds and dihedral angles influence protein configuration.