Final answer:
The expansion of a tract of glutamine in certain proteins is linked to various forms of progressive neurodegeneration, causing proteopathies such as Alzheimer's and Parkinson's diseases.
Step-by-step explanation:
In certain proteins, the expansion of a tract of the amino acid glutamine (E) is associated with various genetic forms of progressive neurodegeneration, such as Huntington's disease. This expansion can result in a protein with altered function, leading to the condition known as a proteopathy, which is when misfolded proteins accumulate and become toxic to cells. The diseases include Alzheimer's and Parkinson's disease, among others, where misfolded proteins play a central role.
The amino acid glutamine is particularly prone to alterations such as deamidation that can contribute to these diseases. Therefore, understanding the role of glutamine in proteins and their stability is of great interest in researching treatments for these debilitating neurodegenerative diseases.