Question

A particular mutant was found that produced a protein that was longer lived than its normal protein. Upon sequencing the mutant, the researcher discovered that specific lysine amino acids had been changed to arginines. Propose a model of what this mutation caused to allow the proteins to be longer lived. Consider how a protein's arginines can be post translationally modified to influence the half-life of the protein.

Answer 1

A mutation that substitutes lysine with arginine in a protein can prolong the protein's half-life by limiting ubiquitin-mediated degradation and may enhance stability through arginine methylation, resulting in a longer-lived protein.

Step-by-step explanation:

A mutation that changes specific lysine amino acids to arginines in a protein can lead to increased protein longevity. This enhancement in protein half-life may be due to the different susceptibilities of lysine and arginine residues to post-translational modifications, such as the addition of ubiquitin. Lysine residues are targets for ubiquitin, and proteins tagged with ubiquitin are directed to the proteasome for degradation. Arginine residues, however, are typically less prone to ubiquitination, leading to a potentially longer-lived protein. Furthermore, arginine can undergo methylation, which may have protective effects against protein degradation, without the presence of lysine, and resulting mutations could therefore hinder the protein's normal turnover, increasing its stability and half-life.