Molecular Weight of the Membrane C5b--9 Complex of Human Complement: Characterization of the Terminal Complex as a C5b--9 Monomer

The hydrodynamic properties of the detergent-solubilized, terminal membrane complex of serum complement components C5--C9 [C5b--9(m)] were studied to obtain an estimate of its molecular weight. In a solution of Triton X-100/deoxycholate, the protein complex binds 17% Triton X-100 and 11% deoxycholat...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 1981-03, Vol.78 (3), p.1818-1822
Main Authors: Bhakdi, Sucharit, Tranum-Jensen, Jørgen
Format: Article
Language:English
Subjects:
Centrifugation
Complement Membrane Attack Complex
Complement System Proteins
Cylinders
Deoxycholic Acid
Detergents
Electron micrographs
Elution
Gels
Humans
Immunology
Macromolecular Substances
Membranes - immunology
Microscopy, Electron
Molecular Weight
Monomers
Octoxynol
Polyethylene Glycols
Protein Binding
Protein Conformation
Proteins
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Summary:The hydrodynamic properties of the detergent-solubilized, terminal membrane complex of serum complement components C5--C9 [C5b--9(m)] were studied to obtain an estimate of its molecular weight. In a solution of Triton X-100/deoxycholate, the protein complex binds 17% Triton X-100 and 11% deoxycholate by weight. The sedimentation coefficient of the protein--detergent complex is 26 S as determined by sucrose density gradient ultracentrifugation, and gel filtration indicated a molecular radius of 11 nm. It was ascertained by electron microscopy that these hydrodynamic parameters apply to mono-dispersed C5b--9(m) complexes, which were observed as nonaggregated, hollow protein cylinders and were identical to the complement ``lesions'' formed on target membranes. The calculated molecular weight of the protein--detergent complex is approximately 1,286,300 to which the protein moiety contributes approximately 1,000,000. The results indicate that the C5b--9(m) complex formed on biological membranes is a monomer entity of the C5--C9 complement components.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.78.3.1818