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O2‐02‐02: TARGETING AMYLOID FORMATION USING RATIONALLY DESIGNED ANTIBODIES
Author(s) -
Aprile Francesco Antonio,
Sormanni Pietro,
Perni Michele,
Arosio Paolo,
Limbocker Ryan,
Chhangur Shianne,
Mannini Benedetta,
Linse Sara,
Knowles Tuomas,
Dobson Christopher M.,
Vendruscolo Michele
Publication year - 2018
Publication title -
alzheimer's and dementia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.713
H-Index - 118
eISSN - 1552-5279
pISSN - 1552-5260
DOI - 10.1016/j.jalz.2018.06.2646
Subject(s) - antibody , epitope , computational biology , amyloid (mycology) , drug discovery , function (biology) , small molecule , biology , peptide , chemistry , immunology , biochemistry , microbiology and biotechnology , botany
mutations within the Ab amino acid sequence for its aggregation. Methods:We used cryo-electron microscopy, solid state NMR spectroscopy and x-ray diffraction to obtain high resolution structural information of fibrils grown from recombinantly expressed Ab(142). Results: We determined the structure of an Ab(1-42) fibril composed of two intertwined protofilaments determined by cryoelectron microscopy (cryo-EM) to 4.0Angstrom resolution, complemented by solid-state nuclear magnetic resonance experiments [1]. The backbone of all 42 residues and nearly all side chains are well resolved in the EM density map, including the entire N terminus, which is part of the cross-b structure resulting in an overall “LS”-shaped topology of individual subunits. The dimer interface protects the hydrophobic C termini from the solvent. The characteristic staggering of the nonplanar subunits results in markedly different fibril ends, termed “groove” and “ridge,” leading to different binding pathways on both fibril ends, which has implications for fibril growth. The b strands are staggered with relation to one another in a zipper-like manner. At both fibril ends, the binding site for the addition of subunit i contains contributions of subunits i1, i-2, i-3, i-4, and i-5, or i+1, i+2, i+3, i+4, and i+5, respectively. Therefore, five Ab(1-42) subunits are required to provide the full interface for monomer addition. For a fragment of six subunits, the capping subunits would have the same full contact interface as those in an extended fibril. We define this structural element of six subunits as the minimal fibril unit. This minimal fibril unit may also be the minimal seed size for nucleation as suggested by results from Ab aggregation studies monitored by small angle neutron scattering and analytical ultracentrifugation. Conclusions: High resolution structural details help to understand the role of amino acid side chains within Ab for fibril formation and growth. [1] Gremer et al., Science 358, 116–119 (2017).