Abstract |
The fluorescence self-quenching by energy transfer of FITC-C9, a fluoresceinated derivative of human complement protein C9 [Sims, P.J. (1984) Biochemistry (preceding paper in this issue)], has been used to monitor the kinetics of C9 polymerization induced by the membrane-associated complex of complement proteins C5b-8. Time-based measurements of the fluorescence change observed during incubation of FITC-C9 with C5b-8-treated sheep red blood cell ghost membranes at various temperatures revealed that C9 polymerization induced by the C5b-8 proteins exhibits a temperature dependence similar to that previously reported for the complement-mediated hemolysis of these cells, with an Arrhenius activation energy for FITC-C9 polymerization of 13.3 +/- 3.2 kcal mol-1 (mean +/- 2 SD). Similar measurements obtained with C5b-8-treated unilamellar vesicles composed of either egg yolk phosphatidylcholine (egg PC), dipalmitoylphosphatidylcholine (DPPC), or dimyristoylphosphatidylcholine ( DMPC) revealed activation energies of between 20 and 25 kcal mol-1 for FITC-C9 polymerization by C5b-8 bound to these membranes. Temperature-dependent rates of C9 polymerization were observed to be largely unaffected by the phase state of membrane lipid in the target C5b-8 vesicles. The significance of these observations of the mechanism of C9 activation of membrane insertion is considered.
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Authors | P J Sims, T Wiedmer |
Journal | Biochemistry
(Biochemistry)
Vol. 23
Issue 14
Pg. 3260-7
(Jul 03 1984)
ISSN: 0006-2960 [Print] United States |
PMID | 6432040
(Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)
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Chemical References |
- Complement C9
- Fluoresceins
- Polymers
- Thiocyanates
- complement C5b-8 complex
- Complement System Proteins
- Fluorescein-5-isothiocyanate
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Topics |
- Animals
- Complement C9
(metabolism)
- Complement System Proteins
(metabolism)
- Erythrocyte Membrane
(metabolism)
- Fluorescein-5-isothiocyanate
- Fluoresceins
- Hemolysis
- Polymers
(metabolism)
- Sheep
- Spectrometry, Fluorescence
- Thiocyanates
- Time Factors
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