The disulfide bonding pattern in ficolin multimers.
Journal Article (Journal Article)
Ficolin is a plasma lectin, consisting of a short N-terminal multimerization domain, a middle collagen domain, and a C-terminal fibrinogen-like domain. The collagen domains assemble the subunits into trimers, and the N-terminal domain assembles four trimers into 12-mers. Two cysteine residues in the N-terminal domain are thought to mediate multimerization by disulfide bonding. We have generated three mutants of ficolin alpha in which the N-terminal cysteines were substituted by serines (Cys4, Cys24, and Cys4/Cys24). The N-terminal cysteine mutants were produced in a mammalian cell expression system, purified by affinity chromatography, and analyzed under nondenaturing conditions to resolve the multimer structure of the native protein and under denaturing conditions to resolve the disulfide-linked structure. Glycerol gradient sedimentation and electron microscopy in nondenaturing conditions showed that plasma and recombinant wild-type protein formed 12-mers. The Cys4 mutant also formed 12-mers, but Cys24 and Cys4/Cys24 mutants formed only trimers. This means that protein interfaces containing Cys4 are stable as noncovalent protein-protein interactions and do not require disulfides, whereas those containing Cys24-Cys24 require the disulfides for stability. Proteins were also analyzed by nonreducing SDS-PAGE to show the covalent structure under denaturing conditions. Wild-type ficolin was covalently linked into 12-mers, whereas elimination of either Cys4 or Cys24 gave dimers and monomers. We present a model in which symmetric Cys24-Cys24 disulfide bonds between trimers are the basis for multimerization. The model may also be relevant to collectin multimers.
Full Text
Duke Authors
Cited Authors
- Ohashi, T; Erickson, HP
Published Date
- February 20, 2004
Published In
Volume / Issue
- 279 / 8
Start / End Page
- 6534 - 6539
PubMed ID
- 14660572
International Standard Serial Number (ISSN)
- 0021-9258
Digital Object Identifier (DOI)
- 10.1074/jbc.M310555200
Language
- eng
Conference Location
- United States