Amyloid fibrils are associated with many fatal degenerative diseases of humans a

Question

Amyloid fibrils are associated with many fatal degenerative diseases of humans and livestock. Livestock diseases such as scrapie in sheep and bovine spongiform encephalitis (BSE, or mad cow disease) have major negative impacts on agriculture. Human diseases characterized by amyloid fibrils include Alzheimer's disease and Creutzfeldt-Jakob disease The images below show a short segment of a typical amyloid fibril. The image on the left shows the side chains protruding from the faces of the ß-sheets. Choose the true statements about amyloid fibrils. Soluble proteins that misfold and form amyloid fibrils become insoluble. Because most newly synthesized proteins fold correctly, the accumulation of misfolded proteins (or fragments) tends to occur slowly, thus explaining the slow onset of disease Proteins that convert to an amyloid fibril structure tend to have low solubility in their native form An amyloid fibril is stabilized by hydrophobic interactions between aromatic residues. An amyloid fibril typically forms from aggregates of misfolded peptides resulting from frameshift mutations

Explanation / Answer

Amyloid fibrils are formed by normally soluble proteins i.e. they are soluble in their native state. These soluble proteins are secreted by cell in misfolded state that causes them to assemble to form insoluble fibers. The misfolding of proteins expose their hydrophobic amino acids which were buried in the protein core. These exposed hydrophobic amino acids form aggregates due to the aqueous nature of the interior of cell. Most of amyloid fibrils have aromatic amino acid residues in core region that stabilize the amyloid structure. Also, most of these proteins fold normally. Thus, the correct statements are

Soluble proteins that misfold and form amyloid fibrils become insoluble

Because most newly synthesized proteins fold correctly, the accumulation of misfolded proteins (or Fragments) tends to occur slowly, thus explaining the slow onset of disease

An amyloid fibril is stabilized by hydrophobic interaction between aromatic amino residues

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