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 Thai, C.-T. Articles by Ogata, R. T. Search for Related Content PubMed PubMed Citation Articles by Thai, C.-T. Articles by Ogata, R. T.

Expression and Characterization of the C345C/NTR Domains of Complement Components C3 and C5 ¹

Torrey Pines Institute for Molecular Studies, San Diego, CA 92121

Complement components C3, C4, and C5 are members of the thioester-containing -macroglobulin protein superfamily. Within this superfamily, a unique feature of the complement proteins is a 150-residue-long C-terminal extension of their -subunits that harbors three internal disulfide bonds. Previous reports have suggested that this is an independent structural module, homologous to modules found in other proteins, including netrins and tissue inhibitors of metalloproteinases. Because of its distribution, this putative module has been named both C345C and NTR. To assess the structures of these segments of the complement proteins, their relationships with other domains, and activities as independent structures, we expressed C345C from C3 and C5 in a bacterial strain that permits cytoplasmic disulfide bond formation. Affinity purification directly from cell lysates yielded recombinant C3- and C5-C345C with properties consistent with multiple intramolecular disulfide bonds and high -sheet contents. rC5-, but not rC3-C345C inhibited complement hemolytic activity, and surface plasmon resonance studies revealed that rC5-C345C binds to complement components C6 and C7 with dissociation constants of 10 and 3 nM, respectively. Our results provide strong evidence that this binding corresponds to the previously described reversible binding of C5 to C6 and C7, and taken together with earlier work, indicate that the C5-C345C module interacts directly with the factor I modules in C6 and C7. The high binding affinities suggest that complexes composed of C5 bound to C6 or C7 exist in plasma before activation and may facilitate assembly of the complement membrane attack complex.

This article has been cited by other articles:

				M. M. Phelan, C.-T. Thai, D. C. Soares, R. T. Ogata, P. N. Barlow, and J. Bramham Solution Structure of Factor I-like Modules from Complement C7 Reveals a Pair of Follistatin Domains in Compact Pseudosymmetric Arrangement J. Biol. Chem., July 17, 2009; 284(29): 19637 - 19649. [Abstract] [Full Text] [PDF]

				C.-T. Thai and R. T. Ogata Recombinant C345C and Factor I Modules of Complement Components C5 and C7 Inhibit C7 Incorporation into the Complement Membrane Attack Complex J. Immunol., May 15, 2005; 174(10): 6227 - 6232. [Abstract] [Full Text] [PDF]

				J. Bramham, C.-T. Thai, D. C. Soares, D. Uhrin, R. T. Ogata, and P. N. Barlow Functional Insights from the Structure of the Multifunctional C345C Domain of C5 of Complement J. Biol. Chem., March 18, 2005; 280(11): 10636 - 10645. [Abstract] [Full Text] [PDF]

				C.-T. Thai and R. T. Ogata Complement Components C5 and C7: Recombinant Factor I Modules of C7 Bind to the C345C Domain of C5 J. Immunol., October 1, 2004; 173(7): 4547 - 4552. [Abstract] [Full Text] [PDF]