Final answer:
Misfolded proteins are targeted for destruction by ubiquitin, which tags them for degradation in the proteasome. Chaperones assist with protein folding but do not destroy misfolded proteins, and methylation and ribonucleases are related to different processes.
Step-by-step explanation:
The process of destroying misfolded proteins after post-translational modification primarily relies on a molecule known as ubiquitin, which targets these defective or excess proteins for degradation. This tagging system involves the attachment of ubiquitin molecules to the misfolded proteins, which then signals for their transportation to a complex called the proteasome. Within the proteasome, the proteins are then broken down and recycled. It's important to note that chaperones assist in the proper folding of proteins but do not directly destroy misfolded ones. Methylation and ribonucleases are involved in different processes such as chemical modification of amino acids and RNA degradation, respectively, and are not directly responsible for the degradation of misfolded proteins. Therefore, for the destruction of misfolded proteins following post-translational modifications, ubiquitin is the correct answer.