Institute of Biochemistry and Molecular Medicine, and Swiss National Centre of Competence in Research (NCCR) TransCure, University of Bern, CH-3012 Bern, Switzerland.
Int J Mol Sci. 2019 Feb 21;20(4):931. doi: 10.3390/ijms20040931.
Heteromeric amino acid transporters (HATs) are protein complexes that catalyze the transport of amino acids across plasma membranes. HATs are composed of two subunits, a heavy and a light subunit, which belong to the solute carrier (SLC) families SLC3 and SLC7. The two subunits are linked by a conserved disulfide bridge. Several human diseases are associated with loss of function or overexpression of specific HATs making them drug targets. The human HAT 4F2hc-LAT2 (SLC3A2-SLC7A8) is specific for the transport of large neutral L-amino acids and specific amino acid-related compounds. Human 4F2hc-LAT2 can be functionally overexpressed in the methylotrophic yeast and pure recombinant protein purified. Here we present the first cryo-electron microscopy (cryo-EM) 3D-map of a HAT, i.e., of the human 4F2hc-LAT2 complex. The structure could be determined at ~13 Å resolution using direct electron detector and Volta phase plate technologies. The 3D-map displays two prominent densities of different sizes. The available X-ray structure of the 4F2hc ectodomain fitted nicely into the smaller density revealing the relative position of 4F2hc with respect to LAT2 and the membrane plane.
杂合氨基酸转运体（HATs）是催化氨基酸跨质膜转运的蛋白复合物。HAT 由两个亚基组成，一个重亚基和一个轻亚基，它们属于溶质载体（SLC）家族 SLC3 和 SLC7。这两个亚基通过保守的二硫键连接。几种人类疾病与特定 HAT 的功能丧失或过度表达有关，使其成为药物靶点。人类 HAT 4F2hc-LAT2（SLC3A2-SLC7A8）特异性转运大中性 L-氨基酸和特定的氨基酸相关化合物。人源 4F2hc-LAT2 可在甲醇营养酵母中功能性过表达，并可纯化得到纯重组蛋白。在这里，我们首次展示了 HAT 的冷冻电镜（cryo-EM）3D 图谱，即人源 4F2hc-LAT2 复合物。该结构使用直接电子探测器和 Volta 相板技术可在~13Å分辨率下确定。3D 图谱显示了两个不同大小的突出密度。4F2hc 外显子的可用 X 射线结构很好地拟合到较小的密度中，揭示了 4F2hc 相对于 LAT2 和膜平面的相对位置。
