Briggs, DC, Birchenough, HL, Ali, T et al. (9 more authors) (2015) Metal Ion-dependent Heavy Chain Transfer Activity of TSG-6 Mediates Assembly of the Cumulus-Oocyte Matrix. Journal of Biological Chemistry, 290 (48). pp. 28708-28723. ISSN 0021-9258
Abstract
The matrix polysaccharide hyaluronan (HA) has a critical role in the expansion of the cumulus cell-oocyte complex (COC), a process that is necessary for ovulation and fertilization in most mammals. Hyaluronan is organized into a cross-linked network by the cooperative action of three proteins, inter-α-inhibitor (IαI), pentraxin-3, and TNF-stimulated gene-6 (TSG-6), driving the expansion of the COC and providing the cumulus matrix with its required viscoelastic properties. Although it is known that matrix stabilization involves the TSG-6-mediated transfer of IαI heavy chains (HCs) onto hyaluronan (to form covalent HC·HA complexes that are cross-linked by pentraxin-3) and that this occurs via the formation of covalent HC·TSG-6 intermediates, the underlying molecular mechanisms are not well understood. Here, we have determined the tertiary structure of the CUB module from human TSG-6, identifying a calcium ion-binding site and chelating glutamic acid residue that mediate the formation of HC·TSG-6. This occurs via an initial metal ion-dependent, non-covalent, interaction between TSG-6 and HCs that also requires the presence of an HC-associated magnesium ion. In addition, we have found that the well characterized hyaluronan-binding site in the TSG-6 Link module is not used for recognition during transfer of HCs onto HA. Analysis of TSG-6 mutants (with impaired transferase and/or hyaluronan-binding functions) revealed that although the TSG-6-mediated formation of HC·HA complexes is essential for the expansion of mouse COCs in vitro, the hyaluronan-binding function of TSG-6 does not play a major role in the stabilization of the murine cumulus matrix.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.. This is an open access article under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits unrestricted use, distribution and reproduction in any medium, provided the original work is properly cited. |
Keywords: | hyaluronan; protein structure; protein-protein interaction; reproduction; site-directed mutagenesis; CUB module structure; TSG-6; cumulus-oocyte complex expansion; heavy chain-hyaluronan complex formation; inter--inhibitor |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Biological Sciences (Leeds) > School of Biomedical Sciences (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 21 Feb 2018 10:09 |
Last Modified: | 21 Feb 2018 10:09 |
Status: | Published |
Publisher: | American Society for Biochemistry and Molecular Biology |
Identification Number: | 10.1074/jbc.M115.669838 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:125601 |