Figure 6: Analysis of amyloid fibrils.

(a) Congo red-stained kidney specimen viewed under fluorescent light source with bright red areas representing amyloid deposits. Purple coloured lines-areas microdissected for MS-based proteomic analysis. (b) Results of MS-based proteomic analysis of amyloid plaques from the kidney and spleen specimens in two independent microdissections. The identified proteins are listed according to their relative abundance, with top 25 from a total of 720 proteins shown. The columns show the protein name, the UnitProt identifier (protein accession number in the UniProt database, http://www.uniprot.org/), the molecular weight of the protein, two microdissections of the kidney specimen and two microdissections of the spleen specimen. The numbers indicate number of total peptide spectra identified for each protein. The amyloid-associated proteins are identified by yellow stars. The peptides representing the serum amyloid A-2 protein (red box) are the primary cause of amyloid deposits in the Sca1-HGAL mouse model. (c) serum amyloid-associated protein-2 (SAA2) protein coverage in the Sca1-HGAL mouse amyloidosis model. The amino-acid (aa) sequence of the SAA2_MOUSE is provided. The yellow highlights indicate the parts of the protein that were identified by the liquid chromatography tandem mass spectrometry. The first 19 aa represent the N terminus signal peptide of the SAA2_MOUSE (red box) cleaved before the mature SAA2_MOUSE is secreted into the circulation, and thus is not expected to be part of the amyloid deposits. The peptides missing in the middle of the protein are unlikely to be detected by liquid chromatography tandem mass spectrometry due to abundance of numerous trypsin cutting sites.