Single-stranded DNA binding properties of three DNA repair proteins (A, B, and C) were investigated. A biotinylated single-stranded DNA was prepared and incubated with the proteins in different combinations as shown below. This was followed by streptavidin pull-down to enrich ssDNA-bound proteins, which were detected by western blot analyses using specific antibodies.

Which one of the following statements is NOT a correct conclusion from the above study?​

Correct option is D

Based on the experimental setup and results from the western blot:

• Protein A is observed to bind to ssDNA.
• Protein B does not show any binding to ssDNA in the western blot analysis.
• Protein C interacts with ssDNA in combination with protein A but does not bind when protein B is present.

Explanation: 

1. Protein A binds to ssDNA: This is correct. The presence of protein A in the pull-down with ssDNA confirms that it binds to ssDNA.

2. Protein B does not bind to ssDNA: This is correct. Since protein B is absent from the pull-down with ssDNA, it indicates that protein B does not interact with ssDNA.

3. Protein C destabilizes the binding of protein A to ssDNA: This is correct. Protein C, when present with protein A, shows disruption in the interaction with ssDNA, suggesting that protein C interferes with or destabilizes protein A's binding to ssDNA.

4. Protein C interacts with Protein A but not with Protein B: This statement is incorrect. The explanation clearly states that although protein C interacts with protein A, it does not show any interaction with protein B based on the experimental evidence. Therefore, this conclusion about protein C's interaction with protein B is not supported.

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