| FRET-based Microscopy Assay to Measure Activity of Membrane Amino Acid Transporters with Single-transporter Resolution
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Author:
Date:
2021-04-05
[Abstract] 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 ...
[摘要] [摘要]次级活性转运蛋白驻留在细胞膜中，利用离子的电化学梯度作为能量源，可针对陡峭的浓度梯度转运极性氨基酸（如氨基酸）。通常，基于集合的放射性标记底物摄取或转运电流的测量可确定转运蛋白的动力学参数。在这里，我们描述了一种基于荧光的谷氨酸和天冬氨酸转运蛋白功能测定方法，该方法使用古细菌升降剂型钠和天冬氨酸共转运蛋白Glt Ph作为模型系统，提供了单转运蛋白，单转运周期的分辨率。我们准备包含重组的纯化的Glt Ph转运蛋白和封装的周质谷氨酸/天冬氨酸结合蛋白，PEB1a，用供体和受体荧光团标记的蛋白脂质体。然后，我们将蛋白脂质体表面固定化，并使用单分子全内反射荧光（TIRF）显微镜测量随时间变化的运输依赖性荧光共振能量转移（FRET）效率变化。与放射性配体摄取测定法相比，该测定法在时间分辨率上提高了10-100倍。它还可以对不同转运周期步骤进行动力学表征，并识别转运蛋白种群内的动力学异质性。
[背景]膜驻留的二级主动转运蛋白或溶质载体（SLC）介导氨基酸，激素，神经递质，维生素和药物等溶质的细胞摄取。他们将集中的底物摄取与主要通过Na + / K + ATPases的作用维持的离子电化学梯度的能量上有利的耗散结合在一起（Lingrel and Kuntzweiler ...
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| Expression and Purification of a Mammalian P2X7 Receptor from Sf9 Insect Cells
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Author:
Date:
2017-09-05
[Abstract] The P2X7 receptor is an extracellular ATP-gated ion channel found only in eukaryotes (Bartlett et al., 2014). Due to its unique properties among P2X receptors, such as formation of a large conductance pore, the P2X7 receptor has been implicated in devastating diseases like chronic pain (North and Jarvis, 2013). However, mechanisms underlying the P2X7 specific properties remain poorly understood, partly because purification of this eukaryotic membrane protein has been challenging. Here we describe a detailed protocol for expressing and purifying a mammalian P2X7 receptor using an insect cell-baculovirus system. The P2X7 receptor is expressed in Sf9 insect cells as a GFP fusion protein and solubilized with a buffer containing Triton X-100 detergent. The P2X7-GFP fusion protein is ...
[摘要] P2X7受体是仅在真核生物中发现的胞外ATP门控离子通道（Bartlett等，2014）。由于其P2X受体之间的独特性质，例如大电导孔的形成，P2X7受体已经涉及破坏性疾病如慢性疼痛（North和Jarvis，2013）。然而，P2X7特异性属性的机制仍然知之甚少，部分原因是纯化这种真核膜蛋白是一个挑战。在这里，我们描述了使用昆虫细胞 - 杆状病毒系统表达和纯化哺乳动物P2X7受体的详细方案。 P2X7受体在作为GFP融合蛋白的Sf9昆虫细胞中表达，并用含有Triton X-100洗涤剂的缓冲液溶解。然后使用Strep-Tactin亲和层析在含有十二烷基麦芽糖苷的缓冲液中纯化P2X7-GFP融合蛋白。在通过凝血酶酶切割连接的GFP和Strep-标签后，使用大小排阻色谱分离P2X7受体。该方法通常从6L的Sf9培养物产生约2mg的纯化蛋白质。纯化的蛋白质可以用含有15％甘油的缓冲液在4℃下储存至少2个月，并用于各种功能和结构研究（Karasawa和Kawate，2016）。
【背景】P2X7受体是嘌呤能P2X受体家族的七种亚型之一，并且是广泛疾病如神经退行性疾病，癫痫和神经性疼痛的有希望的新型药物靶点（North和Jarvis，2013; Bhattacharya和Biber， ...
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| Expression, Purification and Crystallisation of the Adenosine A2A Receptor Bound to an Engineered Mini G Protein
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Author:
Date:
2017-04-20
[Abstract] G protein-coupled receptors (GPCRs) promote cytoplasmic signalling by activating heterotrimeric G proteins in response to extracellular stimuli such as light, hormones and nucleosides. Structure determination of GPCR–G protein complexes is central to understanding the precise mechanism of signal transduction. However, these complexes are challenging targets for structural studies due to their conformationally dynamic and inherently transient nature. We recently developed an engineered G protein, mini-Gs, which addressed these problems and allowed the formation of a stable GPCR–G protein complex. Mini-Gs facilitated the structure determination of the human adenosine A2A receptor (A2AR) in its G protein-bound conformation at 3.4 Å resolution. ...
[摘要] G蛋白偶联受体（GPCR）通过激活异源三聚体G蛋白来响应细胞外刺激如光，激素和核苷来促进细胞质信号传导。 GPCR-G蛋白复合物的结构测定对于了解信号转导的精确机制至关重要。然而，由于它们的构象动态和固有的短暂性质，这些复合物是结构研究的具有挑战性的目标。我们最近开发了一种工程化的G蛋白，微型G ，解决了这些问题，并允许形成稳定的GPCR-G蛋白复合物。 Mini-G 促进了人腺苷A 2A受体（A 2A 2A）在其G蛋白结合构象中的结构测定，在3.4 Å分辨率。在这里，我们描述了A 2A R R的表达和纯化的一步一步的方案，并且A 2AA-R-mini-G'子>复杂。
背景 我们最近开发了一种工程化的最小G蛋白，迷你G（Carpenter和Tate，2016），其促进了人腺苷A 2A受体的结构测定（A <其活性状态（carpenter等人，2016）。 mini-g="">充分稳定A 2A R的活性构象，以允许络合物在洗涤剂辛硫基葡糖苷中通过蒸气扩散结晶。在这里，我们描述了一种用于表达和纯化Aβ2A ...
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