A mutation that changes an alanine residue in the interior...

Name: Problem 16, Chapter 2: Biochemistry
Uploaded: 2020-07-29T21:51:39-08:00
Duration: 2 min 16 s
Channel: Jessica Honkomp
Description: A mutation that changes an alanine residue in the interior of a protein to valine is found to lead to a loss of activity. However, activity is regained when a second mutation at a different position changes an isoleucine residue to glycine. How might this second mutation lead to a restoration of activity?

A mutation that changes an alanine residue in the interior of a protein to valine is found to lead to a loss of activity. However, activity is regained when a second mutation at a different position changes an isoleucine residue to glycine. How might this second mutation lead to a restoration of activity?

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Key Concepts

Protein Tertiary Structure

Protein tertiary structure refers to the three-dimensional arrangement of a protein's amino acid chain, which is held together by various interactions such as hydrogen bonds, ionic bonds, and hydrophobic interactions. Changes in side chain size and properties within the interior of a protein can disrupt the delicate balance of these forces, potentially leading to misfolding or altered conformations that affect the protein's activity.

Hydrophobic Core Packing

The hydrophobic core of a protein is formed by nonpolar side chains that are tightly packed to avoid contact with water. The precise packing of these hydrophobic residues is critical for structural integrity. A mutation that increases side chain bulk can create steric clashes, while a second mutation that decreases the size can alleviate overcrowding, thereby restoring proper packing and function.

Compensatory Mutation

A compensatory mutation occurs when a second mutation counterbalances the detrimental effects of an initial mutation. By adjusting the local environment or geometry of the protein, a compensatory mutation can restore activity by re-establishing favorable intramolecular interactions and relieving structural strain introduced by the first mutation.

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