title: Amino acid sequence surrounding the chondroitin sulfate attachment site of thrombomodulin regulates chondroitin polymerization.
abstract: Thrombomodulin (TM) is a cell-surface glycoprotein and a critical mediator of endothelial anticoagulant function. TM exists as both a chondroitin sulfate (CS) proteoglycan (PG) form and a non-PG form lacking a CS chain (α-TM); therefore, TM can be described as a part-time PG. Previously, we reported that α-TM bears an immature, truncated linkage tetrasaccharide structure (GlcAβ1-3Galβ1-3Galβ1-4Xyl). However, the biosynthetic mechanism to generate part-time PGs remains unclear. In this study, we used several mutants to demonstrate that the amino acid sequence surrounding the CS attachment site influences the efficiency of chondroitin polymerization. In particular, the presence of acidic residues surrounding the CS attachment site was indispensable for the elongation of CS. In addition, mutants defective in CS elongation did not exhibit anti-coagulant activity, as in the case with α-TM. Together, these data support a model for CS chain assembly in which specific core protein determinants are recognized by a key biosynthetic enzyme involved in chondroitin polymerization.
authors.affiliation: Department of Biochemistry, Kobe Pharmaceutical University, Higashinada-ku, Kobe 658-8558, Japan.
authors.forename: Tomomi
authors.initials: T
authors.lastname: Izumikawa
authors.affiliation: Department of Biochemistry, Kobe Pharmaceutical University, Higashinada-ku, Kobe 658-8558, Japan. Electronic address: kitagawa@kobepharma-u.ac.jp.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kitagawa
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D016466:CHO Cells; D002807:Chondroitin / Q000737:chemistry*; D002809:Chondroitin Sulfates / Q000378:metabolism*; D006224:Cricetinae; D003412:Cricetulus; D017931:DNA Primers; D016297:Mutagenesis, Site-Directed; D016133:Polymerase Chain Reaction; D058105:Polymerization; D018180:Thrombomodulin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D017931:DNA Primers; D018180:Thrombomodulin; D002807:Chondroitin; D002809:Chondroitin Sulfates
keywords: Chondroitin sulfate; Extracellular matrix; Glycosaminoglycan; Glycosyltransferase; Proteoglycan