Analysis of functional domains within adhesive proteins with the aim of controlling the interaction between cells and collagens

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Collagen is one of the most common proteins found in extra-cellular matrix (ECM). In ECM there are proteins like collagen which are inherently present there as ECM proteins, and there are proteins which are associated with these ECM proteins and exert respective functions in the associated state. We have been interested in the latter kind of proteins and have been trying to locate the functional domains within these proteins. Followings are the main findings we have made from the research carried out during the last three years using this research grant.(1). We isolated a protein from platelets bound to type I collagen. We identified this protein by N-terminal amino acid sequence analyses as propolypeptide of von Willebrand factor (pp-vWF) which had been called von Willebrand antigen II.(2). We succeeded in narrowing down the collagen binding domain to a ten-residue portion Trp620-Ser629 out of 843 amino acid residues.(3). As the mature von Willebrand factor which is derived from the c … More ommon precursor for pp-vWF is also known to bind to type I collagen, we made a comparison between these two proteins in terms of binding characteristics to the collagen. We came to a conclusion that they recognize different sites in the collagen molecule for the binding.(4). We found that pp-vWF was present not only in alpha-granules but also on the surface of platelets. This may indicate that it plays a role during the adhesion of platelets to collagen present in subendothelium.(5). We found pp-vWF cross-linked to an ECM protein laminin via blood coagulation factor XIIIa or tissue transglutaminase.(6). We then investigated another collagen-binding protein thrombospondin (TSP). TSP was different from pp-vWF in that it preferentially bound to native type V collagen, rather than type I collagen unlike pp-vWF.As we have a future plan of making a comparison between these two collagen binding domains, we studied the type V collagen-binding domain of TSP.We were able to locate the domain to a portion comprised of 80 amino acid residues out of the 450-kDa molecule. Less