Stereospecific amyloid-like fibril formation by a peptide fragment of beta2-microglobulin.
Understanding the role of the L/D-stereospecificity of amino acids is important in obtaining further insight into the mechanism of the formation of amyloid fibrils. Beta(2)-microglobulin is a major component of amyloid fibrils deposited in patients with dialysis-related amyloidosis. A 22-residue peptide of beta(2)-microglobulin, Ser20-Lys41 (L-K3 peptide), obtained by digestion with Acromobacter protease I, formed amyloid-like fibrils in 50% (v/v) 2,2,2-trifluoroethanol and 10 mM HCl at 25 degrees C, as confirmed by thioflavin T fluorescence, circular dichroism spectra, and atomic force microscopy images. A synthetic K3 peptide composed of D-amino acids (D-K3 peptide) formed similar fibrils but with opposite chirality as indicated by circular dichroism spectra. A mixture of L-K3 and D-K3 peptides also formed fibrils, although the L- and D-amino acid composition of each fibril is unknown. To examine the possible cross-reactivity between L- and D-enantiomers, we carried out seeding experiments in which preformed seeds were extended by monomers. The results revealed that only the homologous extensions proceed smoothly, i.e., the growth of L-seeds by L-monomers or D-seeds by D-monomers. The results suggest that, while the fibrils derived from L- and D-peptides form in a similar manner but with opposite stereochemistry, a cross-reaction between them is prevented because the geometry of the mixed sheet cannot satisfy dominant factors for beta-sheet stabilization.
Wadai
Hiromasa
H
Institute for Protein Research, Osaka University, and CREST, Japan Science and Technology Agency, Yamadaoka 3-2, Suita, Osaka 565-0871, Japan.
Yamaguchi
Kei-ichi
K
Takahashi
Satoshi
S
Kanno
Takashi
T
Kawai
Tomoji
T
Naiki
Hironobu
H
Goto
Yuji
Y
D000595:Amino Acid Sequence; D000682:Amyloid / Q000737:chemistry; D000686:Amyloidosis; D002942:Circular Dichroism; D006801:Humans; D007700:Kinetics; D018625:Microscopy, Atomic Force; D008958:Models, Molecular; D010446:Peptide Fragments / Q000737:chemistry; D011487:Protein Conformation; D001613:beta 2-Microglobulin / Q000737:chemistry* / Q000648:ultrastructure
D000682:Amyloid; D010446:Peptide Fragments; D001613:beta 2-Microglobulin