what would happen if you treated a protein (containing 3 S-S bonds) with urea and mercaptoethanol? I know that the urea breaks hydrogen bonds and that the mercaptoethanol reduced disulfide bonds but what levels of the protein would be affected?
When a protein containing 3 S-S bonds is treated with urea and mercaptoethanol, the effects on the protein structure and disulfide bonds can be explained as follows:
1. Urea: Urea is a denaturant that disrupts hydrogen bonding interactions. When urea is added to the protein solution, it can unfold the protein by breaking hydrogen bonds that stabilize its secondary and tertiary structures. This unfolding disrupts the overall protein conformation, leading to loss of its native shape and functional activity.
2. Mercaptoethanol: Mercaptoethanol is a reducing agent that specifically targets disulfide bonds (-S-S-) between cysteine residues in a protein. When mercaptoethanol is added to the protein solution, it donates a hydrogen atom (-H) to each sulfur atom in the disulfide bond, resulting in the formation of two sulfhydryl groups (-SH). The breaking of the disulfide bonds leads to a reduction in the protein's higher-order structure by disrupting its native conformation.
As a result of the treatments with urea and mercaptoethanol, the levels of the protein that would be affected are as follows:
1. Primary Structure: The primary structure of the protein, which refers to the linear sequence of amino acids, remains unaffected by these treatments. The urea and mercaptoethanol primarily act on the higher order structures of the protein.
2. Secondary and Tertiary Structure: The secondary and tertiary structures of the protein are highly dependent on hydrogen bonding interactions. When urea disrupts the hydrogen bonds, the secondary structure (e.g., alpha-helices and beta-sheets) and tertiary structure (3D folding) of the protein are unfolded or denatured.
3. Disulfide Bonding: The treatment with mercaptoethanol specifically targets and reduces the disulfide bonds in the protein. As a result, the protein loses its native conformation and any structural elements that were stabilized by the disulfide bonds are disrupted.
In summary, treating a protein containing 3 S-S bonds with urea and mercaptoethanol would affect the secondary and tertiary structure of the protein, leading to denaturation and disruption of its native conformation. Additionally, the disulfide bonds would be reduced by mercaptoethanol, further affecting the protein's structure.