2otk: Difference between revisions

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[[Image:2otk.jpg|left|200px]]
[[Image:2otk.jpg|left|200px]]


{{Structure
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|RESOURCES=<span class='plainlinks'>[http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=2otk FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=2otk OCA], [http://www.ebi.ac.uk/pdbsum/2otk PDBsum], [http://www.rcsb.org/pdb/explore.do?structureId=2otk RCSB]</span>
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'''Structure of Alzheimer Ab peptide in complex with an engineered binding protein'''
'''Structure of Alzheimer Ab peptide in complex with an engineered binding protein'''
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==Overview==
==Overview==
Affibody (Affibody) ligands specific for human amyloid beta (Abeta) peptides (40 or 42 amino acid residues in size), involved in the progress of Alzheimer's disease, were selected by phage display technology from a combinatorial protein library based on the 58-amino acid residue staphylococcal protein A-derived Z domain. Post-selection screening of 384 randomly picked clones, out of which 192 clones were subjected to DNA sequencing and clustering, resulted in the identification of 16 Affibody variants that were produced and affinity purified for ranking of their binding properties. The two most promising Affibody variants were shown to selectively and efficiently bind to Abeta peptides, but not to the control proteins. These two Affibody ligands were in dimeric form (to gain avidity effects) coupled to affinity resins for evaluation as affinity devices for capture of Abeta peptides from human plasma and serum. It was found that both ligands could efficiently capture Abeta that were spiked (100 microgml(-1)) to plasma and serum samples. A ligand multimerization problem that would yield suboptimal affinity resins, caused by a cysteine residue present at the binding surface of the Affibody ligands, could be circumvented by the generation of second-generation Affibody ligands (having cysteine to serine substitutions). In an epitope mapping effort, the preferred binding site of selected Affibody ligands was mapped to amino acids 30-36 of Abeta, which fortunately would indicate that the Affibody molecules should not bind the amyloid precursor protein (APP). In addition, a significant effort was made to analyze which form of Abeta (monomer, dimer or higher aggregates) that was most efficiently captured by the selected Affibody ligand. By using Western blotting and a dot blot assay in combination with size exclusion chromatography, it could be concluded that selected Affibody ligands predominantly bound a non-aggregated form of analyzed Abeta peptide, which we speculate to be dimeric Abeta. In conclusion, we have successfully selected Affibody ligands that efficiently capture Abeta peptides from human plasma and serum. The potential therapeutic use of these optimized ligands for extracorporeal capture of Abeta peptides in order to slow down or reduce amyloid plaque formation, is discussed.
According to the amyloid hypothesis, the pathogenesis of Alzheimer's disease is triggered by the oligomerization and aggregation of the amyloid-beta (Abeta) peptide into protein plaques. Formation of the potentially toxic oligomeric and fibrillar Abeta assemblies is accompanied by a conformational change toward a high content of beta-structure. Here, we report the solution structure of Abeta(1-40) in complex with the phage-display selected affibody protein Z(Abeta3), a binding protein of nanomolar affinity. Bound Abeta(1-40) features a beta-hairpin comprising residues 17-36, providing the first high-resolution structure of Abeta in beta conformation. The positions of the secondary structure elements strongly resemble those observed for fibrillar Abeta. Z(Abeta3) stabilizes the beta-sheet by extending it intermolecularly and by burying both of the mostly nonpolar faces of the Abeta hairpin within a large hydrophobic tunnel-like cavity. Consequently, Z(Abeta3) acts as a stoichiometric inhibitor of Abeta fibrillation. The selected Abeta conformation allows us to suggest a structural mechanism for amyloid formation based on soluble oligomeric hairpin intermediates.


==About this Structure==
==About this Structure==
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==Reference==
==Reference==
Selection and characterization of Affibody ligands binding to Alzheimer amyloid beta peptides., Gronwall C, Jonsson A, Lindstrom S, Gunneriusson E, Stahl S, Herne N, J Biotechnol. 2007 Jan 30;128(1):162-83. Epub 2006 Sep 27. PMID:[http://www.ncbi.nlm.nih.gov/pubmed/17088007 17088007]
Stabilization of a beta-hairpin in monomeric Alzheimer's amyloid-beta peptide inhibits amyloid formation., Hoyer W, Gronwall C, Jonsson A, Stahl S, Hard T, Proc Natl Acad Sci U S A. 2008 Apr 1;105(13):5099-104. Epub 2008 Mar 28. PMID:[http://www.ncbi.nlm.nih.gov/pubmed/18375754 18375754]
[[Category: Engineered binding protein]]
[[Category: Engineered binding protein]]
[[Category: Homo sapiens]]
[[Category: Homo sapiens]]
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[[Category: Hard, T.]]
[[Category: Hard, T.]]
[[Category: Hoyer, W.]]
[[Category: Hoyer, W.]]
[[Category: beta-hairpin]]
[[Category: Beta-hairpin]]
[[Category: de novo protein]]
[[Category: De novo protein]]
[[Category: intermolecular beta-sheet]]
[[Category: Intermolecular beta-sheet]]
[[Category: peptide binding protein]]
[[Category: Peptide binding protein]]
[[Category: protein-peptide complex]]
[[Category: Protein-peptide complex]]
 
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