It is also possible that Dally and its associated heparan sulfate affect the activity of extracellular enzymes that regulate Dpp. Tolloid, a metalloprotease related to BMP-1, potentiates Dpp activity and could potentially be a target for glycosaminoglycan regulation of its protease activity. Heparin, a short chain glycosaminoglycan synthesized by mast cells and basophils activates the protease inhibitor Antithrombin III, providing a precedent for a glycosaminoglycan controlling extracellular enzyme activity. Whatever the mechanism, cell surface proteoglycans add another dimension to the regulation of growth factor signaling at the cell surface. Because sulfate or carboxyl groups are present on most of their sugar residues, GAGs are highly negatively charged.
GAGs tend to adopt highly extended conformations that occupy a large volume relative to their mass.
Dally shows a similar degree of homology to the different GRIPs as they do to each other.