Ultrastructure of the membrane attack complex of complement: detection of the tetramolecular C9-polymerizing complex C5b-8.

Details

Serval ID
serval:BIB_22034AA6FB37
Type
Article: article from journal or magazin.
Collection
Publications
Institution
Title
Ultrastructure of the membrane attack complex of complement: detection of the tetramolecular C9-polymerizing complex C5b-8.
Journal
Proceedings of the National Academy of Sciences of the United States of America
Author(s)
Tschopp J., Podack E.R., Müller-Eberhard H.J.
ISSN
0027-8424 (Print)
ISSN-L
0027-8424
Publication state
Published
Issued date
1982
Volume
79
Number
23
Pages
7474-7478
Language
english
Abstract
The ultrastructure of the membrane attack complex (MAC) of complement had been described as representing a hollow cylinder of defined dimensions that is composed of the proteins C5b, C6, C7, C8, and C9. After the characteristic cylindrical structure was identified as polymerized C9 [poly(C9)], the question arose as to the ultrastructural identity and topology of the C9-polymerizing complex C5b-8. An electron microscopic analysis of isolated MAC revealed an asymmetry of individual complexes with respect to their length. Whereas the length of one boundary (+/- SEM) was always 16 +/- 1 nm, the length of the other varied between 16 and 32 nm. In contrast, poly(C9), formed spontaneously from isolated C9, had a uniform tubule length (+/- SEM) of 16 +/- 1 nm. On examination of MAC-phospholipid vesicle complexes, an elongated structure was detected that was closely associated with the poly(C9) tubule and that extended 16-18 nm beyond the torus of the tubule and 28-30 nm above the membrane surface. The width of this structure varied depending on its two-dimensional projection in the electron microscope. By using biotinyl C5b-6 in the formation of the MAC and avidin-coated colloidal gold particles for the ultrastructural analysis, this heretofore unrecognized subunit of the MAC could be identified as the tetramolecular C5b-8 complex. Identification also was achieved by using anti-C5 Fab-coated colloidal gold particles. A similar elongated structure of 25 nm length (above the surface of the membrane) was observed on single C5b-8-vesicle complexes. It is concluded that the C5b-8 complex, which catalyzes poly(C9) formation, constitutes a structure of discrete morphology that remains as such identifiable in the fully assembled MAC, in which it is closely associated with the poly(C9) tubule.
Keywords
Complement C9, Complement Membrane Attack Complex, Complement System Proteins/physiology, Liposomes, Macromolecular Substances, Microscopy, Electron, Phosphatidylcholines, Structure-Activity Relationship
Pubmed
Web of science
Open Access
Yes
Create date
24/01/2008 15:19
Last modification date
20/08/2019 12:58
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