3myz

Protein induced photophysical changes to the amyloid indicator dye, thioflavin T

spinqualitylabelsall models 3myz, resolution 1.60Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 3myz is a 2 chain structure with sequence from Homo sapiens. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 1.6Å Ligands: ACT, HG, TFX, TLA Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Disease B2MG_HUMAN Defects in B2M are the cause of hypercatabolic hypoproteinemia (HYCATHYP) [MIM:241600. Affected individuals show marked reduction in serum concentrations of immunoglobulin and albumin, probably due to rapid degradation. Note=Beta-2-microglobulin may adopt the fibrillar configuration of amyloid in certain pathologic states. The capacity to assemble into amyloid fibrils is concentration dependent. Persistently high beta(2)-microglobulin serum levels lead to amyloidosis in patients on long-term hemodialysis. Function B2MG_HUMAN Component of the class I major histocompatibility complex (MHC). Involved in the presentation of peptide antigens to the immune system. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMed The small molecule thioflavin T (ThT) is a defining probe for the identification and mechanistic study of amyloid fiber formation. As such, ThT is fundamental to investigations of serious diseases such as Alzheimer's disease, Parkinson disease, and type II diabetes. For each disease, a different protein undergoes conformational conversion to a beta-sheet rich fiber. The fluorescence of ThT exhibits an increase in quantum yield upon binding these fibers. Despite its widespread use, the structural basis for binding specificity and for the changes to the photophysical properties of ThT remain poorly understood. Here, we report the co-crystal structures of ThT with two alternative states of beta-2 microglobulin (beta2m); one monomeric, the other an amyloid-like oligomer. In the latter, the dye intercalates between beta-sheets orthogonal to the beta-strands. Importantly, the fluorophore is bound in such a manner that a photophysically relevant torsion is limited to a range of angles generally associated with low, not high, quantum yield. Quantum mechanical assessment of the fluorophore shows the electronic distribution to be strongly stabilized by aromatic interactions with the protein. Monomeric beta2m gives little increase in ThT fluorescence despite showing three fluorophores, at two binding sites, in configurations generally associated with high quantum yield. Our efforts fundamentally extend existing understanding about the origins of amyloid-induced photophysical changes. Specifically, the beta-sheet interface that characterizes amyloid acts both sterically and electronically to stabilize the fluorophore's ground state electronic distribution. By preventing the fluorophore from adopting its preferred excited state configuration, nonradiative relaxation pathways are minimized and quantum yield is increased. Protein-induced photophysical changes to the amyloid indicator dye thioflavin T.,Wolfe LS, Calabrese MF, Nath A, Blaho DV, Miranker AD, Xiong Y Proc Natl Acad Sci U S A. 2010 Sep 28;107(39):16863-8. Epub 2010 Sep 8. PMID:20826442 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Beta-2 microglobulin 3D structures

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