Abstract
Mannan-binding lectin (MBL), previously called 'mannan-binding protein' or MBP, is a plasma C-type lectin which, upon binding to carbohydrate structures on micro-organisms, activates the classical pathway of complement. Purification of MBL relies on its Ca(2+)-dependent affinity for carbohydrate, but existing methods are susceptible to contamination by anti-carbohydrate antibodies. In the present study a sequential-sugar-elution method has been developed which can achieve a preparation of virtually pure MBL and its associated serine protease (MBL-associated serine protease, MASP) by two steps of affinity chromatography. In further separation of MASP from MBL, it was found that activated MASP was associated with MBL independent of Ca2+. Since MBL was found to bind to underivatized Sepharose 4B, the MBL-MASP complex was purified using Sepharose 4B and protease inhibitors were included to purify the complex with MASP in its proenzyme form. Analysis of thus-purified MBL-MASP complex by gel filtration on a Sephacryl S-300 column at pH 7.8 showed that the proenzyme MASP was also associated with MBL independently of Ca2+, but that the complex could be disrupted at a low pH (5.0). Therefore the mechanism of MBL-MASP-mediated complement activation appears to be significantly different from the C1-mediated classical pathway.
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- Drickamer K., Dordal M. S., Reynolds L. Mannose-binding proteins isolated from rat liver contain carbohydrate-recognition domains linked to collagenous tails. Complete primary structures and homology with pulmonary surfactant apoprotein. J Biol Chem. 1986 May 25;261(15):6878–6887. [PubMed] [Google Scholar]
- Drickamer K. Engineering galactose-binding activity into a C-type mannose-binding protein. Nature. 1992 Nov 12;360(6400):183–186. doi: 10.1038/360183a0. [DOI] [PubMed] [Google Scholar]
- Drickamer K., Taylor M. E. Biology of animal lectins. Annu Rev Cell Biol. 1993;9:237–264. doi: 10.1146/annurev.cb.09.110193.001321. [DOI] [PubMed] [Google Scholar]
- Fornstedt N., Porath J. Characterization studies on a new lectin found in seeds of Vicia ervilia. FEBS Lett. 1975 Sep 15;57(2):187–191. doi: 10.1016/0014-5793(75)80713-7. [DOI] [PubMed] [Google Scholar]
- Ikeda K., Sannoh T., Kawasaki N., Kawasaki T., Yamashina I. Serum lectin with known structure activates complement through the classical pathway. J Biol Chem. 1987 Jun 5;262(16):7451–7454. [PubMed] [Google Scholar]
- Kawasaki T., Kawasaki N., Yamashina I. Mannose/N-acetylglucosamine-binding proteins from mammalian sera. Methods Enzymol. 1989;179:310–321. doi: 10.1016/0076-6879(89)79133-3. [DOI] [PubMed] [Google Scholar]
- Laemmli U. K. Cleavage of structural proteins during the assembly of the head of bacteriophage T4. Nature. 1970 Aug 15;227(5259):680–685. doi: 10.1038/227680a0. [DOI] [PubMed] [Google Scholar]
- Lu J. H., Thiel S., Wiedemann H., Timpl R., Reid K. B. Binding of the pentamer/hexamer forms of mannan-binding protein to zymosan activates the proenzyme C1r2C1s2 complex, of the classical pathway of complement, without involvement of C1q. J Immunol. 1990 Mar 15;144(6):2287–2294. [PubMed] [Google Scholar]
- Malhotra R., Thiel S., Reid K. B., Sim R. B. Human leukocyte C1q receptor binds other soluble proteins with collagen domains. J Exp Med. 1990 Sep 1;172(3):955–959. doi: 10.1084/jem.172.3.955. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Matsushita M., Fujita T. Activation of the classical complement pathway by mannose-binding protein in association with a novel C1s-like serine protease. J Exp Med. 1992 Dec 1;176(6):1497–1502. doi: 10.1084/jem.176.6.1497. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Miyamura K., Leigh L. E., Lu J., Hopkin J., López Bernal A., Reid K. B. Surfactant protein D binding to alveolar macrophages. Biochem J. 1994 May 15;300(Pt 1):237–242. doi: 10.1042/bj3000237. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Ohta M., Okada M., Yamashina I., Kawasaki T. The mechanism of carbohydrate-mediated complement activation by the serum mannan-binding protein. J Biol Chem. 1990 Feb 5;265(4):1980–1984. [PubMed] [Google Scholar]
- Reid K. B. Proteins involved in the activation and control of the two pathways of human complement. Biochem Soc Trans. 1983 Jan;11(1):1–12. doi: 10.1042/bst0110001. [DOI] [PubMed] [Google Scholar]
- Sim R. B. The human complement system serine proteases C1r and C1s and their proenzymes. Methods Enzymol. 1981;80(Pt 100):26–42. doi: 10.1016/s0076-6879(81)80006-7. [DOI] [PubMed] [Google Scholar]
- Super M., Thiel S., Lu J., Levinsky R. J., Turner M. W. Association of low levels of mannan-binding protein with a common defect of opsonisation. Lancet. 1989 Nov 25;2(8674):1236–1239. doi: 10.1016/s0140-6736(89)91849-7. [DOI] [PubMed] [Google Scholar]
- Takada F., Takayama Y., Hatsuse H., Kawakami M. A new member of the C1s family of complement proteins found in a bactericidal factor, Ra-reactive factor, in human serum. Biochem Biophys Res Commun. 1993 Oct 29;196(2):1003–1009. doi: 10.1006/bbrc.1993.2349. [DOI] [PubMed] [Google Scholar]
- Takayama Y., Takada F., Takahashi A., Kawakami M. A 100-kDa protein in the C4-activating component of Ra-reactive factor is a new serine protease having module organization similar to C1r and C1s. J Immunol. 1994 Mar 1;152(5):2308–2316. [PubMed] [Google Scholar]
- Weis W. I., Drickamer K., Hendrickson W. A. Structure of a C-type mannose-binding protein complexed with an oligosaccharide. Nature. 1992 Nov 12;360(6400):127–134. doi: 10.1038/360127a0. [DOI] [PubMed] [Google Scholar]
- Ziccardi R. J. Nature of the interaction between the C1q and C1r2S2 subunits of the first component of human complement. Mol Immunol. 1985 Apr;22(4):489–494. doi: 10.1016/0161-5890(85)90133-6. [DOI] [PubMed] [Google Scholar]