title: Marfan syndrome-causing mutations in fibrillin-1 result in gross morphological alterations and highlight the structural importance of the second hybrid domain.
abstract: Mutations in fibrillin-1 result in Marfan syndrome, which affects the cardiovascular, skeletal and ocular systems. The multiorgan involvement and wide spectrum of associated phenotypes highlights the complex pathogenesis underlying Marfan syndrome. To elucidate the genotype to phenotype correlations, we engineered four Marfan syndrome causing mutations into a fibrillin-1 fragment encoded by exons 18-25, a region known to interact with tropoelastin. Biophysical and biochemical approaches, including small angle x-ray scattering, analytical ultracentrifugation, and circular dichroism, were used to study the impact of these mutations upon the structure and function of the protein. Mutations G880S, C862R, and C908R, situated within the second hybrid domain, disrupted the ratio of alpha-helix to beta-sheet leading to a more compact conformation. These data clearly demonstrate the importance of the previously uncharacterized hybrid domain in fibrillin-1 structure. In contrast, mutation K1023N situated within the linker region between the third eight cysteine motif and cbEGF 11 markedly extended the length of the fragment. However, none of the mutations affected tropoelastin binding. The profound effects of all four mutations on fragment conformation suggest that they contribute to the pathogenesis of Marfan syndrome by disrupting protein folding and its assembly into fibrillin-rich microfibrils.
authors.affiliation: Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, United Kingdom.
authors.forename: Kieran T
authors.initials: KT
authors.lastname: Mellody
authors.forename: Lyle J
authors.initials: LJ
authors.lastname: Freeman
authors.forename: Clair
authors.initials: C
authors.lastname: Baldock
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Jowitt
authors.forename: Veronique
authors.initials: V
authors.lastname: Siegler
authors.forename: Bertrand D E
authors.initials: BD
authors.lastname: Raynal
authors.forename: Stuart A
authors.initials: SA
authors.lastname: Cain
authors.forename: Tim J
authors.initials: TJ
authors.lastname: Wess
authors.forename: C Adrian
authors.initials: CA
authors.lastname: Shuttleworth
authors.forename: Cay M
authors.initials: CM
authors.lastname: Kielty
mesh_terms: D000595:Amino Acid Sequence; D055592:Biophysical Phenomena; D001703:Biophysics; D000071838:Fibrillin-1; D000071837:Fibrillins; D006801:Humans; D007700:Kinetics; D008382:Marfan Syndrome / Q000235:genetics*; D008840:Microfilament Proteins / Q000737:chemistry / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry; D020349:Surface Plasmon Resonance; D054392:Adipokines
chemical_list: D000071838:Fibrillin-1; D000071837:Fibrillins; D008840:Microfilament Proteins; D011994:Recombinant Proteins; C000605722:FBN1 protein, human; D054392:Adipokines