Photoinduced fibrils formation of chicken egg white lysozyme under native conditions.
Recent findings showed that transiently accessing structurally native-like yet energetically higher conformational states is sufficient to trigger the formation of protein fibrils. Typically, these conformational states are made available through changing solvent conditions or introducing mutations. Here we show a novel way to initialize fibril formation for Chicken egg white lysozyme (CEWL) under native conditions via controlled UV illumination. Through a cassette of tryptophan-based photochemistry, the two terminal disulfide bonds in CEWL can be selectively reduced. The reduced CEWL is then converted to conformational states with the C-terminal fragment floppy upon thermal fluctuation. These states serve as precursors for the fibrillar aggregation. Intriguingly, the CEWL fibrils are stabilized by intermolecular disulfide bonds instead of noncovalent β-sheet structures, distinct from the amyloid-like lysozyme fibrils reported before. Based on the experimental evidences and all-atom molecular dynamics simulation, we proposed a "runaway domain-swapping" model for the structure of the CEWL fibrils, in which each CEWL molecule swaps the C-terminal fragment into the complementary position of the adjacent molecule along the fibrils. We anticipate that this fibrillation mechanism can be extended to many other disulfide-containing proteins. Our study stands for the first example of formation of protein fibrils under native conditions upon UV illumination and poses the potential danger of low UV dose to organisms at the protein level.
National Laboratory of Solid State Microstructure and Department of Physics, Nanjing University, Nanjing 210093, China.
Jin-Bing
JB
Xie
Yi
Y
Cao
Hai
H
Pan
Meng
M
Qin
Zhi-Qiang
ZQ
Yan
Xiang
X
Xiong
Wei
W
Wang
D000595:Amino Acid Sequence; D000682:Amyloid / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D000818:Animals; D002645:Chickens; D004220:Disulfides / Q000737:chemistry / Q000378:metabolism; D057927:Hydrophobic and Hydrophilic Interactions; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009113:Muramidase / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D055668:Photochemical Processes; D011487:Protein Conformation; D017510:Protein Folding; D014466:Ultraviolet Rays
D000682:Amyloid; D004220:Disulfides; C421864:hen egg lysozyme; D009113:Muramidase