Question

In the 1950s, Christian Anfinsen demonstrated the renaturation of the protein ribonuclease (RNase) in vitro. After reduction (to reduce the disulfide links) and the addition of urea (to denature the protein), the protein was in an unfolded state. After removing the urea and the reducing agent, the protein refolded, with greater than 90% activity. If the urea were removed after oxidation occurred, the protein had less than 5% activity. Why would the protein not refold correctly if the urea were removed after the reducing agent was removed? (In other words, what would happen if the urea were removed after oxidation?) Choose the best answer.
(A) Urea would participate in weak bonding interactions with RNase, preventing oxidation of Cys.
(B) The protein would not fully unfold (denature).
(C) Disulfide bonds are not positioned correctly unless weak bonding interactions are present.
(D) Contaminants in the RNase preparation would form covalent bonds with the protein, preventing reactivation.

Answer 1

Answer:

The correct answer to the question: What would happen if the urea were removed after oxidation, would be, C: Disulfide bonds are not positioned correctly unless weak bonding interactions are present.

Explanation:

Christian Anfinsen´s and colleagues´s research on proteins, their structure, their function, and what affects them, yielded information that has impacted the way that proteins are studied today. This research was not only able to find the structure of proteins, but also how this structure was formed, and what would happen if it was affected by different factors, meaning, if the protein would remain functional or not. In his experiment with urea, Anfinsen and his colleagues found that what mattered in protein structure was the fine balance in the elements, called residue, inside the structure, and not those on the outside. They also found that when urea was removed from the protein after oxidation had happened, then the cysteine residue would not be placed correctly inside the structure, thus affecting it and reducing its capacity to perform.