Quaternary structure

Quaternary structure refers to the arrangement of multiple folded protein or coiling protein molecules in a multi-subunit complex. It is the fourth level of protein structure and is concerned with the structure and arrangement of the entire protein complex, including the spatial arrangement of the subunits and the nature of their interactions.

Overview

The quaternary structure is the highest level of organization in a protein complex, and it is the level at which the function of the protein becomes manifest. It is determined by a variety of bonding interactions, including hydrophobic interactions, ionic bonding, hydrogen bonding, and disulfide bridges. These interactions can occur between the different subunits of the protein complex, or they can occur between different parts of the same subunit.

Importance

The quaternary structure is critical for the function of many proteins. For example, the quaternary structure of hemoglobin allows it to carry oxygen in the blood. The quaternary structure of enzymes can also be important for their function, as it can allow for the formation of an active site that is not present in the individual subunits.

Determination

The quaternary structure of a protein can be determined using a variety of techniques, including X-ray crystallography, nuclear magnetic resonance spectroscopy, and cryo-electron microscopy. These techniques can provide detailed information about the arrangement of the subunits in the protein complex, as well as the nature of their interactions.

Examples

Examples of proteins with a quaternary structure include hemoglobin, which is composed of four subunits, and DNA polymerase, which is composed of multiple subunits that work together to replicate DNA.

See also

• Primary structure
• Secondary structure
• Tertiary structure

Quaternary structure Resources
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