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Fig. 8. Schematic model for the proposed role of TNFIP6 in the stabilization of the
cumulus extracellular matrix. For simplicity, only two hyaluronan chains are
shown, but the proposed interactions can crosslink many of these chains
creating a very stable hyaluronan meshwork. Asterisks indicate covalent
interactions (ester bonds) between the heavy chains (HCs) and hyaluronan. All
other protein-hyaluronan interactions are non-covalent. The presence of HC(1
or 2)-TNFIP6 complexes in the cumulus matrix was demonstrated in our previous
study (Mukhopadhyay et al.,
2001). Note that the exact structure of the HC-TNFIP6 has not yet
been elucidated, therefore two hypothetical complex structures are shown. `?'
indicates that no HC3-TNFIP6 complex has been detected yet. CS, chondroitin
sulfate.