| Object: Polypeptide: N-acetylgalactosaminyltransferase-2 (ppGalNAc-T2) is an important member of polypeptide: N-acetylgalactosaminyltransferase (ppGalNAc-T) family.β1,3-N-acetylglucosaminyltransferase/β1,3galactosytransferase(β3Gn-T8 /β3GalT7) is a new member of glycosyltransferases we gained by electric cloning.These two types of glycosyltransferases both play important rolls in the process of O-sugar chain synthesis. Costimulatory molecule B7-H3 is a type-I transmembrane glycoprotein. It has been reported that B7-H3 amino acid sequence has several glycosylation sites. This thesis aims to study the relativity between ppGalNAc-T orβ3Gn-T8/β3GalT7 and costimulatory molecule B7-H3, and the role of ppGalNAc-T2 in the B7-H3 protein O-sugar chain synthesis.Methods: Getting the different molecular structure of two isoforms of costimulatory molecule B7-H3 by homology modeling. Getting the molecular structure ofβ3Gn-T8/β3GalT7 by homology modeling, too. Then combining the two isoforms of B7-H3 protein structure homology model with ppGalNAc-T2 protein structure orβ3Gn-T8/β3GalT7 to find whether they can directly combine. Looking for the potential interaction locus between ppGalNAc-T2 orβ3Gn-T8/β3GalT7 and B7-H3 in order to study the role of ppGalNAc-T2 andβ3Gn-T8/β3GalT7 in the process of B7-H3 protein O-sugar chain synthesis. Co-immunoprecipitation was used to study the combination of ppGalNAc-T2 protein and B7-H3 protein.Results: Successfully simulating the molecular structure of two isoforms of costimulatory molecule B7-H3 and finding it has a possible interaction between ppGalNAc-T2 and B7-H3. Successfully simulating the molecular structure ofβ3Gn-T8/β3GalT7 and finding the potential interaction locus between B7-H3 andβ3Gn-T8/β3GalT7. 4IgB7-H3 protein and ppGalNAc-T2 can combine together in Co-immunoprecipitation. Conclusion: By homology modeling, we simulating the 3D protein structure ofβ3Gn-T8/β3GalT7 and two isoforms of B7-H3 protein. With the structural bioinformatics studying, we find that there are potential locus betweenβ3Gn-T8/β3GalT7 and B7-H3. ppGalNAc-T2 and B7-H3 can directly combine testified by structural bioinformatics studying and co-immunoprecipitation. It has a relativity between ppGalNAc-T2 and B7-H3. ppGalNAc-T2 plays a roll in the B7-H3 protein O-sugar chain synthesis. |
