Apolipoprotein A-I (apoA-I) is the major component of high density lipoproteins and plays a vital role
in reverse cholesterol transport. Lipid-free apoA-I is the main constituent of amyloid deposits found
in atherosclerotic plaques, an acquired type of amyloidosis, whereas its N-terminal fragments have
been associated with a hereditary form, known as familial apoA-I amyloidosis. Here, we identified and
verified four “aggregation-prone” segments of apoA-I with amyloidogenic properties, utilizing electron
microscopy, X-ray fiber diffraction, ATR FT-IR spectroscopy and polarized light microscopy. These segments
may act as conformational switches, possibly controlling the transition of the -helical apoA-I
content into the “cross-” architecture of amyloid fibrils. A structural model illuminating the structure
of amyloid fibrils formed by the N-terminal fragments of apoA-I is proposed, indicating that two of the
identified chameleon segments may play a vital part in the formation of amyloid fibrils in familial apoA-I
amyloidosis.
(EN)
