title: Properties of some variants of human beta2-microglobulin and amyloidogenesis.
abstract: Three variants of human beta(2)-microglobulin (beta(2)-m) were compared with wild-type protein. For two variants, namely the mutant R3Abeta(2)-m and the form devoid of the N-terminal tripeptide (DeltaN3beta(2)-m), a reduced unfolding free energy was measured compared with wild-type beta(2)-m, whereas an increased stability was observed for the mutant H31Ybeta(2)-m. The solution structure could be determined by (1)H NMR spectroscopy and restrained modeling only for R3Abeta(2)-m that showed the same conformation as the parent species, except for deviations at the interstrand loops. Analogous conclusions were reached for H31Ybeta(2)-m and DeltaN3beta(2)-m. Precipitation and unfolding were observed over time periods shorter than 4-6 weeks with all the variants and, sometimes, with wild-type protein. The rate of structured protein loss from solution as a result of precipitation and unfolding always showed pseudo-zeroth order kinetics. This and the failure to observe an unfolded species without precipitation suggest that a nucleated conformational conversion scheme should apply for beta(2)-m fibrillogenesis. The mechanism is consistent with the previous and present results on beta(2)-m amyloid transition, provided a nucleated oligomeric species be considered the stable intermediate of fibrillogenesis, the monomeric intermediate being the necessary transition step along the pathway from the native protein to the nucleated oligomer.
authors.affiliation: Dipartimento di Scienze e Tecnologie Biomediche and Microgravity, Aging, Training, and Immobility, Centre of Excellence, Università di Udine, Piazzale Kolbe 4, 33100 Udine, Italy.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Corazza
authors.forename: Fabio
authors.initials: F
authors.lastname: Pettirossi
authors.forename: Paolo
authors.initials: P
authors.lastname: Viglino
authors.forename: Giuliana
authors.initials: G
authors.lastname: Verdone
authors.forename: Julian
authors.initials: J
authors.lastname: Garcia
authors.forename: Pascal
authors.initials: P
authors.lastname: Dumy
authors.forename: Sofia
authors.initials: S
authors.lastname: Giorgetti
authors.forename: Palma
authors.initials: P
authors.lastname: Mangione
authors.forename: Sara
authors.initials: S
authors.lastname: Raimondi
authors.forename: Monica
authors.initials: M
authors.lastname: Stoppini
authors.forename: Vittorio
authors.initials: V
authors.lastname: Bellotti
authors.forename: Gennaro
authors.initials: G
authors.lastname: Esposito
mesh_terms: D000682:Amyloid / Q000378:metabolism; D000686:Amyloidosis / Q000378:metabolism; D006801:Humans; D008958:Models, Molecular; D009154:Mutation; D011487:Protein Conformation; D011489:Protein Denaturation; D013329:Structure-Activity Relationship; D001613:beta 2-Microglobulin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D000682:Amyloid; D001613:beta 2-Microglobulin