Question

Why are proteins that adopt non-native conformations generally insoluble?

A) Non-native conformations disrupt hydrogen bonding.
B) Non-native conformations disrupt hydrophobic interactions.
C) Non-native conformations increase protein stability.
D) Non-native conformations increase protein solubility.

Answer 1

Proteins with non-native conformations are insoluble due to the disruption of hydrophobic interactions that expose hydrophobic regions to water, leading to aggregation. The native folding pattern minimizes these interactions and maintains solubility, which is lost upon denaturation.

Step-by-step explanation:

Proteins that adopt non-native conformations are generally insoluble because these conformations disrupt hydrophobic interactions. In their native state, proteins fold in such a way that the hydrophobic R groups of nonpolar amino acids are sequestered away from the aqueous environment, buried in the interior of the protein's structure. When proteins are in non-native conformations, this intricate balance is disturbed, causing the hydrophobic regions to be exposed to water, which leads to aggregation and insolubility.

Denaturation of proteins involves the disruption of hydrogen bonds, disulfide linkages, salt bridges, and hydrophobic interactions that normally stabilize the protein's structure. Because nonpolar groups cannot engage in hydrogen bonding, a native protein folding pattern minimizes contact with water through hydrophobic interactions, thus maintaining solubility.

In the case of protein denaturation, the hydrophobic parts of the protein that are normally hidden, come into contact with the water, causing the protein molecules to clump together and precipitate out of solution, thereby reducing solubility.

Answer 2

Proteins that adopt non-native conformations generally insoluble because B) Non-native conformations disrupt hydrophobic interactions.

Step-by-step explanation:

Proteins that adopt non-native conformations are generally insoluble due to the disruption of hydrophobic interactions. Hydrophobic interactions play a crucial role in maintaining the three-dimensional structure of proteins. In their native state, proteins have hydrophobic amino acid residues that are typically buried in the interior of the protein, shielded from the surrounding water molecules. This hydrophobic core stabilizes the protein structure by minimizing the exposure of hydrophobic residues to the aqueous environment.

When proteins adopt non-native conformations, these hydrophobic interactions are disrupted, leading to exposure of the hydrophobic residues to water. Since water molecules strongly interact with each other through hydrogen bonding, they tend to exclude nonpolar substances like hydrophobic amino acid residues. This results in a decrease in protein solubility as the exposed hydrophobic regions become unfavorable in the aqueous environment, causing the protein to aggregate or precipitate.

In summary, the disruption of hydrophobic interactions in non-native conformations leads to increased exposure of hydrophobic residues to water, making the proteins less soluble. This phenomenon is a consequence of the hydrophobic effect, a thermodynamic driving force that influences the folding and solubility of proteins in aqueous environments.