title: A non-natural variant of human lysozyme (I59T) mimics the in vitro behaviour of the I56T variant that is responsible for a form of familial amyloidosis.
abstract: We report here the detailed characterisation of a non-naturally occurring variant of human lysozyme, I59T, which possesses a destabilising point mutation at the interface of the alpha- and beta-domains. Although more stable in its native structure than the naturally occurring variants that give rise to a familial form of systemic amyloidosis, I59T possesses many attributes that are similar to these disease-associated species. In particular, under physiologically relevant conditions, I59T populates transiently an intermediate in which a region of the structure unfolds cooperatively; this loss of global cooperativity has been suggested to be a critical feature underlying the amyloidogenic nature of the disease-associated lysozyme variants. In the present study, we have utilised this variant to provide direct evidence for the generic nature of the conformational transition that precedes the ready formation of the fibrils responsible for lysozyme-associated amyloid disease. This non-natural variant can be expressed at higher levels than the natural amyloidogenic variants, enabling, for example, singly isotopically labelled protein to be generated much more easily for detailed structural studies by multidimensional NMR spectroscopy. Moreover, we demonstrate that the I59T variant can readily form fibrils in vitro, similar in nature to those of the amyloidogenic I56T variant, under significantly milder conditions than are needed for the wild-type protein.
authors.affiliation: Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK.
authors.forename: Christine L
authors.initials: CL
authors.lastname: Hagan
authors.forename: Russell J K
authors.initials: RJ
authors.lastname: Johnson
authors.forename: Anne
authors.initials: A
authors.lastname: Dhulesia
authors.forename: Mireille
authors.initials: M
authors.lastname: Dumoulin
authors.forename: Janice
authors.initials: J
authors.lastname: Dumont
authors.forename: Erwin
authors.initials: E
authors.lastname: De Genst
authors.forename: John
authors.initials: J
authors.lastname: Christodoulou
authors.forename: Carol V
authors.initials: CV
authors.lastname: Robinson
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Dobson
authors.forename: Janet R
authors.initials: JR
authors.lastname: Kumita
mesh_terms: D000682:Amyloid / Q000378:metabolism; D028226:Amyloidosis, Familial / Q000201:enzymology / Q000235:genetics*; D041961:Deuterium Exchange Measurement; D006801:Humans; D008958:Models, Molecular; D009113:Muramidase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D019906:Nuclear Magnetic Resonance, Biomolecular; D017354:Point Mutation; D013816:Thermodynamics
chemical_list: D000682:Amyloid; D009113:Muramidase
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