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Mutations in the human fibrillin-1 (FBN-1) gene cause Marfan syndrome (MFS), an autosomal dominant disease of connective tissue. Fibrillin-1, a 350 kDa extracellular calcium binding protein, is a major structural component of 10-12 nm microfibrils and consists predominantly of two repeated module types: the calcium binding epidermal growth factor-like (cbEGF) domain and the transforming growth factor beta1 binding protein-like (TB) domain. A group of reported FBN-1 mutations is predicted to reduce calcium binding to cbEGF domains by removal of a side chain ligand for calcium. These mutations occur in two protein domain contexts, either in a cbEGF preceded by a TB domain or in a cbEGF preceded by another cbEGF domain. In this study we have used three proteases to probe structural changes caused by an N2144S MFS calcium binding mutation in a TB6-cbEGF32 and a cbEGF32-33 domain pair, and an N2183S mutation in the cbEGF32-33 pair. N-terminal sequence analysis of domain pairs digested in the presence and absence of calcium show that: (i) domain interactions between TB6 and cbEGF32 are calcium independent, despite the presence of a calcium binding site in cbEGF32; (ii) domain interactions between cbEGF32 and cbEGF33 are calcium dependent; and (iii) an N-->S mutation causes increased proteolytic susceptibility only when located in cbEGF33, consistent with a key role for interdomain calcium binding in rigidifying cbEGF domain linkages. These data demonstrate for the first time that the structural consequences of calcium binding mutations in fibrillin-1 cbEGF domains can be influenced by domain context.

Type

Journal article

Journal

Hum Mol Genet

Publication Date

12/08/2000

Volume

9

Pages

1987 - 1994

Keywords

Calcium, Calcium-Binding Proteins, Extracellular Matrix Proteins, Fibrillin-1, Fibrillins, Fibrinolysin, Humans, Marfan Syndrome, Microfilament Proteins, Mutation, Missense, Pancreatic Elastase, Protein Structure, Secondary, Protein Structure, Tertiary, Trypsin