Secondary active transporters reside in cell membranes transporting polar solutes like amino acids against steep concentration gradients, using electrochemical gradients of ions as energy sources. Commonly, ensemble-based measurements of radiolabeled substrate uptakes or transport currents inform on kinetic parameters of transporters. Here we describe a fluorescence-based functional assay for glutamate and aspartate transporters that provides single-transporter, single-transport cycle resolution using an archaeal elevator-type sodium and aspartate symporter GltPh as a model system. We prepare proteo-liposomes containing reconstituted purified GltPh transporters and an encapsulated periplasmic glutamate/aspartate-binding protein, PEB1a, labeled with donor and acceptor fluorophores. We then

Connexins are membrane bound proteins that facilitate direct and local paracrine mediated cell-to-cell communication through their ability to oligomerise into hexameric hemichannels. When neighbouring channels align, they form gap-junctions that provide a direct route for information transfer between cells. In contrast to intact gap junctions, which typically open under physiological conditions, undocked hemichannels have a low open probability and mainly open in response to injury. Hemichannels permit the release of small molecules and ions (approximately 1kDa) into the local intercellular environment, and excessive expression/activity has been linked to a number of disease conditions. Carboxyfluorescein dye uptake measures functional expression of hemichannels, where increased ... [摘要]  [摘要]连接蛋白是有助于直接和局部旁分泌通过自己的能力介导的细胞-细胞通信膜结合蛋白寡聚成六聚半通道。当相邻通道对齐时，它们形成间隙连接，为单元之间的信息传输提供直接路径。与通常在生理条件下打开的完整的间隙连接相反，未对接的半通道的打开概率较低，主要是在受伤时打开。半通道允许小分子和离子（约1kDa）释放到局部细胞间环境中，并且过度表达/活性 与许多疾病状况有关。羧基荧光素染料的摄取量度了半通道的功能性表达，其中增加的半通道活性/功能反映了增加的负荷。该技术依赖于通过开放性半通道对不可渗透膜的荧光示踪剂的吸收，可用于比较在不同条件下（例如对照与疾病）培养的细胞单层之间的通道活性。其他技术（例如生物素化和电生理学）可以分别测量细胞表面表达和半通道开放可能性，但是，羧基荧光素的摄取提供了一种简单，快速且经济高效的方法来测定多种细胞类型的体外半通道活性。


图形摘要：

使用染料吸收量度半通道活性

[背景]连接蛋白（CX ）是一体的跨膜蛋白，其寡聚到连接子在细胞表面。连接子与相似的六聚体蛋白复合物停靠在相邻细胞上，形成用于间隙连接细胞间通讯的双向导管（GJIC；Bosco等人，2011 ...