You are studying the function of a protein isolated from a lung tumor cell line and comparing it to the same protein from normal tissue. You find that the protein derived from the cancer cells does not carry out its correct function as a result of improper folding of the protein. Which of the following, involved in the prevention of aggregation and improper folding of newly synthesized proteins, is most likely to be defective in the lung cancer cells?
A) chaperones
B) lysozymes
C) mitochondrial precursor proteins
D) ribosomal-binding proteins
E) zymogens

Question

Quizplus · Accepted Answer

Chaperones are proteins that assist in the proper folding of other proteins and prevent aggregation, which is crucial for maintaining protein function. If chaperones are defective, proteins may misfold, leading to loss of function, as observed in the cancer cells. Nearly all proteins of the organelles along the secretory pathway, as well as proteins that are expressed at the cell surface or secreted from the cell, are first cotranslationally translocated into the lumen of the endoplasmic reticulum (ER) as unfolded polypeptide chains. Immediately after entering the ER, they are often modified with N-linked glycans, folded into the appropriate secondary and tertiary structures, and finally in many cases are assembled into multimeric complexes. These processes are aided and monitored by ER chaperones and any loss of ER chaperone activity will result in misfolded and potentially aggregated proteins.

You Are Studying the Function of a Protein Isolated from a Lung