ガレクチン‐１：多量体構造とポリラクトサミンとの相互作用

DOI Web Site 被引用文献1件
  • Cho Moonjae
    Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center Oklahoma City
  • Cummings Richard D.
    Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center Oklahoma City
  • 篠原 康郎
    ファルマシアバイオテク (株)研究開発室

書誌事項

タイトル別名
  • Galectin-1: Oligomeric Structure and Interactions with Polylactosamine.
  • ガレクチン 1 タリョウタイ コウゾウ ト ポリラクトサミン ト ノ ソウゴ

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Galectin-1 is a member of the galectin-1 family of lectins that is able to form a homodimer of 14kDa subunits and each subunit has a single carbohydrate-binding site. The lectin is unusual in that it is synthesized in the cytosol of mammalian cells where it accumulates in a monomeric form. The lectin is actively, but slowly secreted (t1/2≈20h), and the secreted form requires glycoconjugate ligands to properly fold and acquire stability. The functional lectin exists in a monomer-dimer equilibrium with a Kd of -7μM and the equilibration rate is rather slow (t1/2≈10h). To explore the mechanism of dimerization and functional differences between monomeric and dimeric forms of the galectin-1, specific mutations were made in the extreme N-terminus involved in subunit interactions. Two of these mutants, termed N-Gal-1 and V5D-Gal-1, are functional monomers at low concentrations (<60μM), but they dimerize at high concentrations. The dimeric forms of native and mutated galectin-1 can be covalently cross-linked to generate nondissociable forms of galectin-1 that are extremely potent agglutinins. In contrast, the monomeric forms lack agglutinating activity, but they can compete with the dimeric forms of the lectin and block binding of the dimers.<br>Galectin-1 binds to lactose Galβ1→4Glc and N-acetyllactosamine Galβ1→4GlcNAc with relatively low affinity (Kd in the range of 90-100μM), but the lectin binds to glycoproteins containing polylactosamine sequences [→3Galβ1→4GlcNAcβ1→]n with high affinity (Kd≈1μM). The lectin does not require terminal non-reducing galactose residues in polylactosamines for recognition. Polylactosamine sequences are selectively expressed on glycoproteins, such as laminin and lysosome-associated membrane proteins (LAMPs). The glycoproteins selectively recognized by galectin-1 may serve as potential ligands through which the lectin promotes cellular adhesion and cell signaling.

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