Model for Protofibril Formation of Beta-2 microglobulin

1) Beta strand A remains folded in this model, unlike previous models. Strand G (residues 83-99) forms the beta sheet core. A type I hairpin is centered at Pro90, Lys91. The sheets are 10.5 Angstroms apart each with a twist of -7 degrees and a pitch (rise per 360 degree turn) of 246 Angstroms (4.77 Angstroms rise per strand, 50 strands per turn). The diameter of the fibril varies between 60-85 Angstroms, not including the unfolded strand A. This model differs from b2m4 only in strand A conformation. The two sheets are entirely antiparallel and form continuous hydrogen bonding pattern along the length of the fibril axis.

2) The asymmetric unit of the fibril is composed of four subunits. Purple, violet, yellow and cream.

3) Color by H/D exchange profile of amyloid fibrils according to Hoshino et al., 2002. Red is protected fully. Blue is protected partially. White is unprotected. Yellow is untested. The problem here is that the central core sheets of this model are mapped to residues that have a high H/D exchange rate (white).

4) Color Magda's peptide in green The entire length of Magda's peptide is involved the central beta sheet core.

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