title: Self-association of the galectin-9 C-terminal domain via the opposite surface of the sugar-binding site.
abstract: Galectin-9 is a lectin, which has various biological functions such as T-cell differentiation and apoptosis. Multivalency of carbohydrate binding is required for galectin-9 to function. Although galectin-1 (a proto-type galectin) forms an oligomer to obtain its multivalency, galectin-9 (a tandem-repeat-type one) has two carbohydrate recognition domains (CRD) in one polypeptide. However, a single CRD of galectin-9, especially the C-terminal one, exhibited pro-apoptotic activity suggesting oligomer formation capability. In this study, we monitored the nuclear magnetic resonance (NMR) signals of the backbone atoms of the galectin-9 C-terminal CRD (G9CCRD). Protein concentration dependence of the signals suggested that a region (F1-F4 strands) opposite to the ligand-binding site was involved in the self-association of G9CCRD. Site-directed mutagenesis in this region (Leu210, Trp277 and Leu279 to Thr; G9CCRD-3T) inhibited the self-association of G9CCRD, and improved the solubility, whereas it reduced its pro-apoptotic activity towards T cells. The high pro-apoptotic activity of G9CCRD seems to be due to the ability to form an oligomer. In addition, the same substitution in two-CRD-containing galectin-9 (G9Null-3T) also diminished the self-association and improved its solubility, although it hardly reduced the anti-proliferative and pro-apoptotic activities. G9CCRD contributes the self-association of full-length galectin-9 at high protein concentrations.
authors: Department of Endocrinology, Kagawa University, Miki-cho, Kita-gun, Kagawa 761-0793, Japan.
authors: Yasuhiro
authors: Y
authors: Nonaka
authors: Takashi
authors: T
authors: Ogawa
authors: Souichi
authors: S
authors: Oomizu
authors: Shin-Ichi
authors: S
authors: Nakakita
authors: Nozomu
authors: N
authors: Nishi
authors: Shigehiro
authors: S
authors: Kamitori
authors: Mitsuomi
authors: M
authors: Hirashima
authors: Takanori
authors: T
authors: Nakamura
mesh_terms: D002460:Cell Line; D037161:Galectins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D019169:Jurkat Cells; D009682:Magnetic Resonance Spectroscopy; D016297:Mutagenesis, Site-Directed; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D013601:T-Lymphocytes / Q000166:cytology / Q000378:metabolism
chemical_list: D037161:Galectins