HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Gadjeva, M. Articles by Law, S. K. A. Search for Related Content PubMed PubMed Citation Articles by Gadjeva, M. Articles by Law, S. K. A.

The Covalent Binding Reaction of Complement Component C3¹

Mihaela Gadjeva^2,*, Alister W. Dodds^*, Aiko Taniguchi-Sidle, Antony C. Willis^*, David E. Isenman and S. K. Alex Law^3,*

^* The Medical Research Council Immunochemistry Unit, Department of Biochemistry, University of Oxford, Oxford, United Kingdom, and Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada

The covalent binding of C3 to target molecules on the surfaces of pathogens is crucial in most complement-mediated activities. When C3 is activated, the acyl group is transferred from the sulfhydryl of the internal thioester to the hydroxyl group of the acceptor molecule; consequently, C3 is bound to the acceptor surface by an ester bond. It has been determined that the binding reaction of the B isotype of human C4 uses a two-step mechanism. Upon activation, a His residue first attacks the internal thioester to form an acyl-imidazole bond. The freed thiolate anion of the Cys residue of the thioester then acts as a base to catalyze the transfer of the acyl group from the imidazole to the hydroxyl group of the acceptor molecule. In this article, we present results which indicate that this two-step reaction mechanism also occurs in C3.

This article has been cited by other articles:

				J. Mutsuro, N. Tanaka, Y. Kato, A. W. Dodds, T. Yano, and M. Nakao Two Divergent Isotypes of the Fourth Complement Component from a Bony Fish, the Common Carp (Cyprinus carpio) J. Immunol., October 1, 2005; 175(7): 4508 - 4517. [Abstract] [Full Text] [PDF]

				H. Boshra, A. E. Gelman, and J. O. Sunyer Structural and Functional Characterization of Complement C4 and C1s-Like Molecules in Teleost Fish: Insights into the Evolution of Classical and Alternative Pathways J. Immunol., July 1, 2004; 173(1): 349 - 359. [Abstract] [Full Text] [PDF]

				E. Jelezarova, A. Luginbuehl, and H. U. Lutz C3b2-IgG Complexes Retain Dimeric C3 Fragments at All Levels of Inactivation J. Biol. Chem., December 19, 2003; 278(51): 51806 - 51812. [Abstract] [Full Text] [PDF]

				A. Verschoor, M. A. Brockman, M. Gadjeva, D. M. Knipe, and M. C. Carroll Myeloid C3 Determines Induction of Humoral Responses to Peripheral Herpes Simplex Virus Infection J. Immunol., November 15, 2003; 171(10): 5363 - 5371. [Abstract] [Full Text] [PDF]

				M. Lin, D. R. Sutherland, W. Horsfall, N. Totty, E. Yeo, R. Nayar, X.-F. Wu, and A. C. Schuh Cell surface antigen CD109 is a novel member of the alpha 2 macroglobulin/C3, C4, C5 family of thioester-containing proteins Blood, March 1, 2002; 99(5): 1683 - 1691. [Abstract] [Full Text] [PDF]