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?
Treating a protein containing three disulfide bonds with urea and mercaptoethanol would have specific effects on the protein's structure. Let's break it down step by step:
1. Urea: Urea is a denaturant that disrupts the non-covalent interactions in proteins, such as hydrogen bonding. When a protein is treated with urea, it unfolds, and the secondary and higher-order structures are disrupted. Urea disrupts the hydrogen bonds that stabilize the protein, leading to the unfolding and loss of its native conformation.
2. Mercaptoethanol: Mercaptoethanol is a reducing agent that specifically targets the disulfide bonds, which are covalent bonds formed between two cysteine residues in a protein. By adding mercaptoethanol, the disulfide bonds are broken, leading to the reduction of cysteine residues.
So, when you combine urea and mercaptoethanol treatment, you would observe the following effects:
- Urea would disrupt the non-covalent interactions in the protein, leading to the unfolding and loss of secondary and higher-order structures.
- Mercaptoethanol would specifically reduce the disulfide bonds, breaking the covalent bonds between cysteine residues.
As a result, the treated protein would be unfolded and devoid of its original structure, and the disulfide bonds would be reduced. The levels of protein affected would be the secondary and higher-order structures and the covalent bonds involved in the disulfide bond formation. The primary structure (amino acid sequence) of the protein would remain intact, as urea and mercaptoethanol do not directly affect the peptide backbone or the amino acid sequence.