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Secondary structure in the core of amyloid fibrils formed from human ??m and its truncated variant ?N6.

ABSTRACT: Amyloid fibrils formed from initially soluble proteins with diverse sequences are associated with an array of human diseases. In the human disorder, dialysis-related amyloidosis (DRA), fibrils contain two major constituents, full-length human ?2-microglobulin (h?2m) and a truncation variant, ?N6 which lacks the N-terminal six amino acids. These fibrils are assembled from initially natively folded proteins with an all antiparallel ?-stranded structure. Here, backbone conformations of wild-type h?2m and ?N6 in their amyloid forms have been determined using a combination of dilute isotopic labeling strategies and multidimensional magic angle spinning (MAS) NMR techniques at high magnetic fields, providing valuable structural information at the atomic-level about the fibril architecture. The secondary structures of both fibril types, determined by the assignment of ~80% of the backbone resonances of these 100- and 94-residue proteins, respectively, reveal substantial backbone rearrangement compared with the location of ?-strands in their native immunoglobulin folds. The identification of seven ?-strands in h?2m fibrils indicates that approximately 70 residues are in a ?-strand conformation in the fibril core. By contrast, nine ?-strands comprise the fibrils formed from ?N6, indicating a more extensive core. The precise location and length of ?-strands in the two fibril forms also differ. The results indicate fibrils of ?N6 and h?2m have an extensive core architecture involving the majority of residues in the polypeptide sequence. The common elements of the backbone structure of the two proteins likely facilitates their ability to copolymerize during amyloid fibril assembly.

SUBMITTER: Su Y

PROVIDER: S-EPMC4017606 | biostudies-literature | 2014 Apr

REPOSITORIES: biostudies-literature

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Secondary structure in the core of amyloid fibrils formed from human β₂m and its truncated variant ΔN6.

Su Yongchao Y Sarell Claire J CJ Eddy Matthew T MT Debelouchina Galia T GT Andreas Loren B LB Pashley Clare L CL Radford Sheena E SE Griffin Robert G RG

Journal of the American Chemical Society 20140416 17

Amyloid fibrils formed from initially soluble proteins with diverse sequences are associated with an array of human diseases. In the human disorder, dialysis-related amyloidosis (DRA), fibrils contain two major constituents, full-length human β2-microglobulin (hβ2m) and a truncation variant, ΔN6 which lacks the N-terminal six amino acids. These fibrils are assembled from initially natively folded proteins with an all antiparallel β-stranded structure. Here, backbone conformations of wild-type hβ ...[more]

PMID: 24679070

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Project description:The persistence of high concentrations of beta-2-microglobulin (β2M) in the blood of patients with acute renal failure leads to the development of the dialysis-related amyloidosis. This disease manifests in the deposition of amyloid fibrils formed from the various forms of β2M in the tissues and biological fluids of patients. In this paper, the amyloid fibrils formed from the full-length β2M (β2m) and its variants that lack the 6 and 10 N-terminal amino acids of the protein polypeptide chain (ΔN6β2m and ΔN10β2m, respectively) were probed by using the fluorescent dye thioflavin T (ThT). For this aim, the tested solutions were prepared via the equilibrium microdialysis approach. Spectroscopic analysis of the obtained samples allowed us to detect one binding mode (type) of ThT interaction with all the studied variants of β2M amyloid fibrils with affinity ~10⁴ M-1. This interaction can be explained by the dye molecules incorporation into the grooves that were formed by the amino acids side chains of amyloid protofibrils along the long axis of the fibrils. The decrease in the affinity and stoichiometry of the dye interaction with β2M fibrils, as well as in the fluorescence quantum yield and lifetime of the bound dye upon the shortening of the protein amino acid sequence were shown. The observed differences in the ThT-β2M fibrils binding parameters and characteristics of the bound dye allowed to prove not only the difference of the ΔN10β2m fibrils from other β2M fibrils (that can be detected visually, for example, by transmission electron microscopy (TEM), but also the differences between β2m and ΔN6β2m fibrils (that can not be unequivocally confirmed by other approaches). These results prove an essential role of N-terminal amino acids of the protein in the formation of the β2M amyloid fibrils. Information about amyloidogenic protein sequences can be claimed in the development of ways to inhibit β2M fibrillogenesis for the treatment of dialysis-related amyloidosis.

Dataset Information

Secondary structure in the core of amyloid fibrils formed from human ??m and its truncated variant ?N6.

Publications

Secondary structure in the core of amyloid fibrils formed from human β₂m and its truncated variant ΔN6.

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