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 Kojouharova, M. S. Articles by Hoppe, H.-J. Search for Related Content PubMed PubMed Citation Articles by Kojouharova, M. S. Articles by Hoppe, H.-J.

Differential Binding of IgG and of a HIV gp41 Peptide by the B Chain and A Chain Globular Head Sequences of C1q, Respectively¹

Mihaela S. Kojouharova^*, Ivelin D. Panchev^*, Magdalena I. Tchorbadjieva^*, Kenneth B. M. Reid^2, and Hans-Jürgen Hoppe

^* Department of Biochemistry, Sofia University "St. Climent Ohridsky," Sofia, Bulgaria; and Medical Research Council Immunochemistry Unit, Department of Biochemistry, University of Oxford, Oxford, United Kingdom

Two individual globular head regions (ghA and ghB) of the heterotrimeric C1q molecule (containing A, B, and C chains) were expressed in a bacterial expression system using a coproduction with the bacterial chaperone GroESL. The purified proteins were soluble and monomeric, as shown by gel-filtration analysis. No association into homotrimers was seen, which indicates that the ability to form heterotrimers is coupled with the discrimination against homotrimeric self-association. The individual globular heads retained their binding activities toward two ligands bound by the whole C1q molecule, i.e., IgG and the peptide P(601–613) derived from the HIV envelope glycoprotein gp41. The differential binding activities displayed for these ligands indicated a degree of structural independence of the binding sites from the regions responsible for heterotrimerization. It was found, using single chain recombinant anti-C1q Abs, that the binding sites on C1q for IgG and gp41 do not overlap, and this observation is also consistent with the view that specialization between the C1q polypeptide chains takes place within the C1q molecule regarding their ligand-binding activities.

This article has been cited by other articles:

				M. S. Kojouharova, M. G. Gadjeva, I. G. Tsacheva, A. Zlatarova, L. T. Roumenina, M. I. Tchorbadjieva, B. P. Atanasov, P. Waters, B. C. Urban, R. B. Sim, et al. Mutational Analyses of the Recombinant Globular Regions of Human C1q A, B, and C Chains Suggest an Essential Role for Arginine and Histidine Residues in the C1q-IgG Interaction J. Immunol., April 1, 2004; 172(7): 4351 - 4358. [Abstract] [Full Text] [PDF]

				C. Gaboriaud, J. Juanhuix, A. Gruez, M. Lacroix, C. Darnault, D. Pignol, D. Verger, J. C. Fontecilla-Camps, and G. J. Arlaud The Crystal Structure of the Globular Head of Complement Protein C1q Provides a Basis for Its Versatile Recognition Properties J. Biol. Chem., November 21, 2003; 278(47): 46974 - 46982. [Abstract] [Full Text] [PDF]

				U. Kishore, S. K. Gupta, M. V. Perdikoulis, M. S. Kojouharova, B. C. Urban, and K. B. M. Reid Modular Organization of the Carboxyl-Terminal, Globular Head Region of Human C1q A, B, and C Chains J. Immunol., July 15, 2003; 171(2): 812 - 820. [Abstract] [Full Text] [PDF]

				U. Kishore, P. Strong, M. V. Perdikoulis, and K. B. M. Reid A Recombinant Homotrimer, Composed of the {{alpha}} Helical Neck Region of Human Surfactant Protein D and C1q B Chain Globular Domain, Is an Inhibitor of the Classical Complement Pathway J. Immunol., January 1, 2001; 166(1): 559 - 565. [Abstract] [Full Text] [PDF]