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Antibody-independent interaction between the first component of human complement, C1, and the outer membrane of Escherichia coli D31 m4
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| Zeitschriftentitel: | Biochemical Journal |
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| Personen und Körperschaften: | , , , |
| In: | Biochemical Journal, 232, 1985, 2, S. 513-519 |
| Format: | E-Article |
| Sprache: | Englisch |
| veröffentlicht: |
Portland Press Ltd.
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| Schlagwörter: |
| Zusammenfassung: | <jats:p>The heptoseless mutant of Escherichia coli, E. coli D31 m4, binds C1q and C1 at 0 degrees C and at low ionic strength (I0.07). Under these conditions, the maximum C1q binding averages 3.0 × 10(5) molecules per bacterium, with a Ka of 1.4 × 10(8) M-1. Binding involves the collagen-like region of C1q, as shown by the capacity of C1q pepsin-digest fragments to bind to E. coli D31 m4, and to compete with native C1q. Proenzyme and activated forms of C1 subcomponents C1r and C1s and their Ca2+-dependent association (C1r-C1s)2 do not bind to E. coli D31 m4. In contrast, the C1 complex binds very effectively, with an average fixation of 3.5 × 10(5) molecules per bacterium, and a Ka of 0.25 × 10(8) M-1, both comparable with the values obtained for C1q binding. C1 bound to E. coli D31 m4 undergoes rapid activation at 0 degrees C. The activation process is not affected by C1-inhibitor, and only slightly inhibited by p-nitrophenyl p'-guanidinobenzoate. No turnover of the (C1r-C1s)2 subunit is observed. Once activated, C1 is only partially dissociated by C1-inhibitor. Our observations are in favour of a strong association between C1 and the outer membrane of E. coli D31 m4, involving mainly the collagen-like moiety of C1.</jats:p> |
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| Umfang: | 513-519 |
| ISSN: |
0264-6021
1470-8728 |
| DOI: | 10.1042/bj2320513 |