ABSTRACT
When protein structures become disrupted, for example in response to chemical damage or physical stress, they unfold and tend to aggregate. Similar unfolding and aggregating behavior is displayed by proteins that are not necessarily damaged but have unusual surface features or abnormal conformations, such as a few intrinsically unstable proteins, mutant proteins, unbound subunits of multimeric complexes, proteins that have lost stabilizing ligands, and proteins that are in a foreign intracellular milieu. Because unfolded proteins can interfere with the functioning of normal proteins, quality control over protein conformation and structure is important for cell growth.
