Structure and Function of SWEET Sugar Transporters

项目摘要 过去十年的研究已经揭示了大量的蛋白质的生理重要性和疾病相关性。 膜转运蛋白/受体超家族，称为MtN 3家族。例如，SWEET转运蛋白是至关重要的 PQ环转运蛋白与胱氨酸病和Batten病有关; 线粒体丙酮酸载体控制着中枢代谢途径的关键分支点， KDEL受体对内质网质量控制至关重要， 扩张型心肌病尽管有这些多样而重要的功能，我们仍然对 MtN 3转运蛋白的分子机制。我们的总体目标是提供结构和机制 阐明跨膜运输的物理基础，并阐明生理学 MtN 3转运蛋白的功能和致病故障。我们将重点关注甜糖转运蛋白， MtN 3家族的创始成员，然后将我们的工作扩展到包括相关的转运蛋白家族。在 我们先前的研究，我们解决了第一个真核SWEET结构在一个向内开放的状态和高分辨率 多种构象状态下的细菌半SWEETS结构，揭示了糖通过 更广泛地说，SWEEE和交替访问机制。这些结果为进一步研究提供了坚实的基础。 探讨MtN 3转运蛋白的作用机制。在这次更新申请中，我们建议将这项工作扩展到：（1） 阐明真核SWEET的串扰和交替通路的结构基础;（2）解剖底物 SWEET转运蛋白的选择性;和（3）确定PQ环转运蛋白的结构基础。 了解MtN 3转运蛋白在分子水平上的工作方式将为其转运提供丰富的见解 机制和串扰。此外，本研究还为进一步了解PQ环的功能提供了一个蓝图 转运蛋白，并解开破坏性溶酶体贮积病的潜在机制。最终，我们的工作 将产生有助于靶向MtN 3治疗的基本知识。 !

PROJECT SUMMARY Research over the past decade has uncovered the physiological importance and disease relevance of a large membrane transporter/receptor superfamily, called the MtN3 clan. For example, SWEET transporters are critical for sugar efflux and utilization; PQ-loop transporters have been linked to cystinosis and Batten disease; the mitochondrial pyruvate carrier controls a critical branch point of the central metabolic pathway and is implicated in cancer; and KDEL receptors are crucial for endoplasmic reticulum quality control and have been associated with dilated cardiomyopathy. Despite these diverse and important functions, we still know little about the molecular mechanisms of MtN3 transporters. Our overall objective is to provide structural and mechanistic insights that elucidate the physical basis of cross-membrane transport and shed light on the physiological functions and disease-causing malfunctions of MtN3 transporters. We will focus on SWEET sugar transporters, the founding members of the MtN3 family, and then expand our work to include related transporter families. In our prior research, we solved the first eukaryotic SWEET structure in an inward-open state and high-resolution structures of bacterial SemiSWEETS in multiple conformation states, shedding light on sugar transport by SWEETs and the alternating access mechanism more broadly. These results provide a solid foundation to further probe the mechanisms of MtN3 transporters. In this renewal application, we propose to extend this work to: (1) elucidate the structural basis of crosstalk and alternating access of eukaryotic SWEET; (2) dissect the substrate selectivity of SWEET transporters; and (3) determine the structural basis of the PQ-loop transporter. Understanding how MtN3 transporters work at the molecular level will provide rich insights into their transport mechanisms and crosstalk. Moreover, this work will provide a blueprint to understand the function of PQ-loop transporters and unravel the mechanisms underlying devasting lysosomal storage diseases. Ultimately, our work will produce essential knowledge that will facilitate targeting MtN3s for therapeutics. !