Membrane attack complex of complement: Generation of high-affinity phospholipid binding sites by fusion of five hydrophilic plasma proteins

E. R. Podack, G. Biesecker, H. J. Muller-Eberhard

Research output: Contribution to journalArticlepeer-review

57 Scopus citations

Abstract

The molecular basis of the membranolytic activity of the membrane attack complex (MAC) of complement was investigated. By using density gradient equilibrium ultracentrifugation, the binding of egg yolk lecithin to the isolated MAC and to its intermediate complexes and precursor proteins was measured. No stable phospholipid-protein complexes were formed with the MAC precursor components C5b-6, C7, C8, and C9. Stable complexes of phospholipid and protein were formed by C5b-7, C5b-8, C5b-9, and the MAC (C5b-9 dimer) and they exhibited densities of 1.2164, 1.184, 1.2055, and 1.2275 g/ml, respectively. The molar phospholipid/protein ratios for the four complexes were determined to be: C5b-7, 399:1; C5b-8, 841:1; C5b-9, 918:1, and C5b-9 dimer, 1460:1. Electron microscopy of the isolated phospholipid-protein complexes revealed no lipid bilayer structures. The magnitude of the phospholipid binding capacity of the MAC is consistent with the interpretation that the MAC forms phospholipid-protein mixed in micelles in lipid bilayers and biological membranes and thus causes formation of hydrophilic lipid channels.

Original languageEnglish (US)
Pages (from-to)897-901
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Volume76
Issue number2
DOIs
StatePublished - 1979

ASJC Scopus subject areas

  • General

Fingerprint Dive into the research topics of 'Membrane attack complex of complement: Generation of high-affinity phospholipid binding sites by fusion of five hydrophilic plasma proteins'. Together they form a unique fingerprint.

Cite this