Book of Abstracts: Albany 2009
June 16-20 2009
© Adenine Press (2008)
The Structure and Morphology of Amyloid Fibrils Depend on Protein Disulfide Bonds
Disulfide bonds play an important role in stabilizing proteins in its native physiologically active conformation. The integrity of protein disulfide bonds could be compromised in cell environment due to the presence of free transitional metals like cupper and iron, hydrogen peroxide and reactive oxygen species etc. Reduced or disrupted disulfide bonds could lead to the misfolding and aggregation of protein molecules, including formation of fibrillar aggregates associated with neurodegenerative diseases such as Alzheimer?s disease (AD), Parkinson?s disease (PD), Huntington?s diseases (HD), prion disease and type II diabetes. We hypothesized that the presence or absence of disulfide bonds in proteins is an important factor which determines the structure and morphology of amyloid fibrils, insoluble aggregates with regular cross-β-structure founded in organs and tissues of patients with neurodegenerative diseases. Amyloid fibrils are noncrystalline and insoluble that limits the application of classical tools of structural biology such as X-ray crystallography and solution NMR. Deep ultraviolet resonance Raman (DUVRR) spectroscopy has been proven to be an efficient technique for characterizing structure of amyloid fibrils. It exhibits unique sensitivity to protein secondary structures and confidently distinguishes main structural elements including α-helix, β-sheet, and random coil conformations. In this study, we used DUVRR spectroscopy, atomic force microscopy (AFM), and CD spectrocopy for comparing the structure of amyloid fibrils formed from apo-α-lactalbumin, a small milk whey protein of most mammals species, with four intact disulfide bonds and 1-SS-carboxymethillactalbumin, in which just one disulfide bond is preserved. We found that both proteins formed fibrils after prolonged incubation in acidic medium, but the morphology of the resulting fibril polymorphs is different. By combining DUVRR spectroscopy with hydrogen deuterium exchange we also demonstrated that the fibril core of the polymorphs had different structure. The obtained results might have an important biomedical meaning because different fibril polymorphs could have different toxicity and accordingly play different roles in pathological processes of degenerative diseases.