title: Structure of the preamyloid dimer of beta-2-microglobulin from covalent labeling and mass spectrometry.
abstract: Beta-2-microglobulin (beta2m) self-associates into fibrillar amyloid deposits in the musculoskeletal system of patients undergoing hemodialysis treatment. Previous studies have shown that stoichiometric amounts of Cu(II) at near physiological conditions can cause beta2m to organize into native-like dimers prior to forming amyloid fibrils. Here, we report the results from selective covalent labeling reactions combined with mass spectrometry that provide insight into the amino acid residues that mediate dimer formation in the wild-type protein. Using three complementary covalent labeling reagents, we find that the dimer interface is formed by the antiparallel stacking of ABED beta-sheets from two beta2m monomers. In addition, our data clearly indicate that a dimer interface involving the interactions of D-D strands from separate protein units as seen in the recent crystal structures of two mutant beta2m oligomers is unlikely.
authors.affiliation: Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003, USA.
authors.forename: Vanessa Leah
authors.initials: VL
authors.lastname: Mendoza
authors.forename: Kwasi
authors.initials: K
authors.lastname: Antwi
authors.forename: Mario A
authors.initials: MA
authors.lastname: Barón-Rodríguez
authors.forename: Cristian
authors.initials: C
authors.lastname: Blanco
authors.forename: Richard W
authors.initials: RW
authors.lastname: Vachet
mesh_terms: D000596:Amino Acids / Q000737:chemistry; D000682:Amyloid / Q000096:biosynthesis* / Q000737:chemistry*; D000818:Animals; D002417:Cattle; D002645:Chickens; D003300:Copper / Q000378:metabolism; D006736:Horses; D006801:Humans; D025941:Protein Interaction Mapping / Q000295:instrumentation / Q000379:methods; D055503:Protein Multimerization; D017433:Protein Structure, Secondary; D021241:Spectrometry, Mass, Electrospray Ionization; D013194:Staining and Labeling; D013499:Surface Properties; D053719:Tandem Mass Spectrometry; D001613:beta 2-Microglobulin / Q000096:biosynthesis* / Q000737:chemistry* / Q000378:metabolism
chemical_list: D000596:Amino Acids; D000682:Amyloid; D001613:beta 2-Microglobulin; D003300:Copper