Division of Gastroenterology, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, 75 Francis Street, Boston, MA, 02115, USA.
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 240 Longwood Avenue, Boston, MA, 02115, USA.
Sci Rep. 2018 Nov 30;8(1):17512. doi: 10.1038/s41598-018-35754-0.
T-cell immunoglobulin and mucin domain containing protein-3 (TIM-3) is an important immune regulator. Here, we describe a novel high resolution (1.7 Å) crystal structure of the human (h)TIM-3 N-terminal variable immunoglobulin (IgV) domain with bound calcium (Ca) that was confirmed by nuclear magnetic resonance (NMR) spectroscopy. Significant conformational differences were observed in the B-C, C'-C″ and C'-D loops of hTIM-3 compared to mouse (m)TIM-3, hTIM-1 and hTIM-4. Further, the conformation of the C-C' loop of hTIM-3 was notably different from hTIM-4. Consistent with the known metal ion-dependent binding of phosphatidylserine (PtdSer) to mTIM-3 and mTIM-4, the NMR spectral analysis and crystal structure of Ca-bound hTIM-3 revealed that residues in the hTIM-3 F-G loop coordinate binding to Ca. In addition, we established a novel biochemical assay to define hTIM-3 functionality as determined by binding to human carcinoembryonic antigen cell adhesion molecule 1 (CEACAM1). These studies provide new insights useful for understanding and targeting hTIM-3.
T 细胞免疫球蛋白和粘蛋白结构域蛋白 3（TIM-3）是一种重要的免疫调节剂。在这里，我们描述了人（h）TIM-3 N 端可变免疫球蛋白（IgV）结构域与钙（Ca）结合的新型高分辨率（1.7Å）晶体结构，该结构通过核磁共振（NMR）光谱得到证实。与鼠（m）TIM-3、hTIM-1 和 hTIM-4 相比，hTIM-3 的 B-C、C'-C″ 和 C'-D 环中观察到显著的构象差异。此外，hTIM-3 的 C-C' 环的构象明显不同于 hTIM-4。与已知的鼠 TIM-3 和鼠 TIM-4 中磷酸丝氨酸（PtdSer）与金属离子依赖性结合一致，Ca 结合的 hTIM-3 的 NMR 光谱分析和晶体结构表明，hTIM-3 的 F-G 环中的残基与 Ca 配位结合。此外，我们建立了一种新的生化测定法来定义 hTIM-3 的功能，该功能通过与人癌胚抗原细胞黏附分子 1（CEACAM1）结合来确定。这些研究为理解和靶向 hTIM-3 提供了新的见解。
