Site-directed mutations in the C-terminal extension of human alphaB-crystallin affect chaperone function and block amyloid fibril formation.
BACKGROUND
Alzheimer's, Parkinson's and Creutzfeldt-Jakob disease are associated with inappropriate protein deposition and ordered amyloid fibril assembly. Molecular chaperones, including alphaB-crystallin, play a role in the prevention of protein deposition.


RESULTS
A series of site-directed mutants of the human molecular chaperone, alphaB-crystallin, were constructed which focused on the flexible C-terminal extension of the protein. We investigated the structural role of this region as well as its role in the chaperone function of alphaB-crystallin under different types of protein aggregation, i.e. disordered amorphous aggregation and ordered amyloid fibril assembly. It was found that mutation of lysine and glutamic acid residues in the C-terminal extension of alphaB-crystallin resulted in proteins that had improved chaperone activity against amyloid fibril forming target proteins compared to the wild-type protein.


CONCLUSIONS
Together, our results highlight the important role of the C-terminal region of alphaB-crystallin in regulating its secondary, tertiary and quaternary structure and conferring thermostability to the protein. The capacity to genetically modify alphaB-crystallin for improved ability to block amyloid fibril formation provides a platform for the future use of such engineered molecules in treatment of diseases caused by amyloid fibril formation.
Treweek
Teresa M
TM
Department of Chemistry, University of Wollongong, Wollongong, New South Wales, Australia.
Ecroyd
Heath
H
Williams
Danielle M
DM
Meehan
Sarah
S
Carver
John A
JA
Walker
Mark J
MJ
D000682:Amyloid / Q000737:chemistry*; D003062:Codon; D018698:Glutamic Acid / Q000737:chemistry; D006801:Humans; D008239:Lysine / Q000737:chemistry; D018832:Molecular Chaperones / Q000737:chemistry; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization; D013696:Temperature; D038203:alpha-Crystallin B Chain / Q000737:chemistry*
D000682:Amyloid; D003062:Codon; D018832:Molecular Chaperones; D011506:Proteins; D038203:alpha-Crystallin B Chain; D018698:Glutamic Acid; D008239:Lysine