期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2004
卷号：101
期号：12
页码：4089-4093
DOI：10.1073/pnas.0305798101
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Although a diversity of proteins is known to form amyloid fibers, their common mechanisms are not clear. Here, we show that an intrinsically unfolded protein (U), represented by a disulfide-deficient variant of hen lysozyme with no tertiary structure, forms an amyloid-like fibril after prolonged incubation. Using variable pressure NMR along with sedimentation velocity, circular dichroism, and fluorescence measurements, we show that, before the fibril formation, the protein forms a pressure-dissociable, soluble assemblage ([IMG]f1.gif" ALT="Formula" BORDER="0">) with a sedimentation coefficient of 17 S and a rich intermolecular {beta}-sheet structure. The reversible assemblage is characterized with a Gibbs energy for association of -23.3 {+/-} 0.8 kJ{middle dot}mol-1 and a volume increase of 52.7 {+/-} 11.3 ml{middle dot}mol-1 per monomer unit, and involves preferential interaction of hydrophobic residues in the initial association step. These results indicate that amyloid fibril formation can proceed from an intrinsically denatured protein and suggest a scheme [IMG]f2.gif" ALT="Formula" BORDER="0"> as a common mechanism of fibril formation in amyloidogenic proteins, where two-way arrows represent reversible processes, one-way arrow represents an irreversible process, and N, U, and [IMG]f1.gif" ALT="Formula" BORDER="0"> represent, respectively, the native conformer, the unfolded monomeric conformer, and the soluble assemblage of unfolded conformers.
