Department of Biology and Chemistry, Liberty University, 1971 University Blvd, Lynchburg, VA 24502, USA.
Department of Biology and Chemistry, Liberty University, 1971 University Blvd, Lynchburg, VA 24502, USA.
Biochim Biophys Acta Gen Subj. 2023 Dec;1867(12):130490. doi: 10.1016/j.bbagen.2023.130490. Epub 2023 Oct 14.
The yeast S. cerevisiae preferably metabolizes glucose through aerobic glycolysis. Glucose transport is facilitated by multiple hexose transporters (Hxts), and their expression and activity are tightly regulated by multiple mechanisms. However, detailed structural and functional analyses of Hxts remain limited, largely due to the lack of crystal structure.
Homology modeling was used to build a 3D structural model for the yeast glucose transporter Hxt1 and investigate the effects of site directed mutations on Hxt1 stability and glucose transport activity.
The conserved salt bridge-forming residues observed in the human Glut4 and the yeast glucose receptor Rgt2 were identified within and between the two 6-transmembrane spanning segments of Hxt1. Most of the RGT2 mutations that disrupt the salt bridge networks were known to cause constitutive signal generation, whereas the corresponding substitutions in HXT1 were shown to decrease Hxt1 stability. While substitutions of the two residues in the salt bridge 2 in Glut4-E329Q and E393D-were reported to abolish glucose transport, the equivalent substitutions in Hxt1 (D382Q and E454D) did not affect Hxt1 glucose transport activity.
Substitutions of equivalent salt bridge-forming residues in Hxt1, Rgt2, and Glut4 are predicted to lock them in an inward-facing conformation but lead to different functional consequences.
The salt bridge networks in yeast and human glucose transporters and yeast glucose receptors may play different roles in maintaining their structural and functional integrity.
酵母 S. cerevisiae 优先通过有氧糖酵解代谢葡萄糖。葡萄糖的运输是由多个己糖转运蛋白（Hxts）促进的，其表达和活性受到多种机制的严格调控。然而，由于缺乏晶体结构，对 Hxts 的详细结构和功能分析仍然有限。
同源建模用于构建酵母葡萄糖转运蛋白 Hxt1 的 3D 结构模型，并研究定点突变对 Hxt1 稳定性和葡萄糖转运活性的影响。
在 Hxt1 的两个 6 跨膜跨段内和之间观察到与人 Glut4 和酵母葡萄糖受体 Rgt2 中保守的盐桥形成残基。大多数破坏盐桥网络的 RGT2 突变已知会导致组成型信号产生，而 HXT1 中的相应取代会降低 Hxt1 的稳定性。虽然 Glut4-E329Q 和 E393D 中的两个残基的盐桥 2 的取代被报道会破坏葡萄糖转运，但 Hxt1 中的等效取代（D382Q 和 E454D）不会影响 Hxt1 的葡萄糖转运活性。
Hxt1、Rgt2 和 Glut4 中盐桥形成残基的取代预计会将它们锁定在内向构象，但导致不同的功能后果。
酵母和人葡萄糖转运蛋白以及酵母葡萄糖受体中的盐桥网络可能在维持其结构和功能完整性方面发挥不同的作用。
