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The structural and mechanistic basis of K(+) translocation by the KtrAB system

KtrAB 系统 K( ) 易位的结构和机制基础

基本信息

批准号：
248766510
负责人：
Professorin Dr. Inga Hänelt
金额：
--
依托单位：
Institut für Biochemie
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2014
资助国家：
德国
起止时间：
2013-12-31 至 2016-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/248766510?language=en
关键词：
structural mechanistic basis translocation KtrAB

项目摘要

The superfamily of K(+) transporters (SKT) units proteins from all kingdoms of life but animals that translocate K(+) and/or Na(+) over the plasma membrane. These proteins are key components of osmotic regulation, pH homeostasis and resistance to high salinity and dryness. SKT proteins are closely related to K(+) channels like KcsA but also show several striking differences which are assigned to an altered function. Within the SKT proteins eukaryotic members consist of only the translocating subunit while prokaryotic members are regulated by at least one additional cytoplasmic subunit. The current hypothesis is that the translocating subunits of prokaryotic members alone show channel-like activities while the regulatory subunits may mediate transporter activity to the system as needed to fulfill its physiological role. Here, we will study the Na(+)-dependent K(+)-translocating KtrAB system of bacteria, in which KtrB is the K(+)-translocating subunit and KtrA mediates Na(+) dependency, K(+) specificity and an increase in uptake velocity. KtrB was shown to contain a unique sequence motif for gating but the structure - function relationship of the system remained unsolved. By use of X-ray crystallography, EPR measurements, transport and electrophysiological measurements we will elucidate the questions (i) which structural and by that also functional impact KtrA has on KtrB, (ii) which mechanisms control K(+) flux within the system on a molecular level and (iii) whether Na(+) acts as ligand to activate channeling or is co-transported as coupling ion.

K（+）转运蛋白（SKT）超家族是除动物外所有生命界的蛋白质单位，其在质膜上转运K（+）和/或Na（+）。这些蛋白质是渗透调节、pH稳态和抗高盐度和干燥的关键组分。SKT蛋白与KcsA等K（+）通道密切相关，但也显示出几个显著的差异，这些差异被分配给改变的功能。在SKT蛋白中，真核生物成员仅由易位亚基组成，而原核生物成员由至少一个额外的胞质亚基调节。目前的假设是，原核成员的易位亚基单独显示通道样活动，而调节亚基可能介导转运活性的系统，需要履行其生理作用。在此，我们将研究细菌的Na（+）依赖性K（+）转运KtrAB系统，其中KtrB是K（+）转运亚基，KtrA介导Na（+）依赖性、K（+）特异性和摄取速度的增加。KtrB被证明含有一个独特的序列基序门控，但系统的结构-功能关系仍然没有解决。通过使用X射线晶体学，EPR测量，运输和电生理测量，我们将阐明的问题（i）的结构和功能的影响KtrA对KtrB，（ii）的机制控制K（+）在分子水平上的系统内的流量和（iii）是否Na（+）作为配体激活通道或共运输耦合离子。