CRYSTAL STRUCTURE DETERMINATION OF YEAST GET3

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 尾锚定蛋白（Tail-anchored protein，TA）是一类跨膜蛋白，其C末端含有一个跨膜螺旋（约25个残基）。TA蛋白如何将TMD插入到膜中的机制与充分研究的共翻译插入途径不同，共翻译插入途径由胞质信号识别颗粒（SRP）介导。TA蛋白翻译后插入内质网膜需要高尔基体内质网运输（GET）复合物，其中包含Get 1，Get 2和Get 3。Get 3是一种ATP酶，可以识别并结合TA蛋白的C-末端跨膜结构域（TMD）。GET复合物如何完成TA蛋白的膜插入尚不清楚。最近，我们已经确定了酵母Get 3晶体结构的开放构象。结构分析表明，Get 3在无核苷酸状态下可能呈开放构象，在ATP结合状态下可能呈闭合构象。Get 3在开放和闭合构象之间转换的构象变化可能有助于TA蛋白的膜插入。Get 3可能具有与ABC转运蛋白相似的转运结合配体的机制。现在我们正在请求光束时间来确定闭合构象中的Get 3晶体结构，以证实我们的假设。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Tail-anchored (TA) proteins represent a unique family of transmembrane proteins which contain a single transmembrane helix (about 25 residues) at the C-terminus. The mechanisms how the TA proteins insert the TMD into membranes are distinct from the well-studied co-translational insertion pathway, which is mediated by the cytosolic signal recognition particle (SRP). The post-translational insertion of the TA proteins into ER membrane requires the Golgi ER trafficking (GET) complex which contains Get1, Get2 and Get3. Get3 is an ATPase and can recognize and bind the C- terminal transmembrane domain (TMD) of the TA proteins. It is not well understood how GET complex accomplish the membrane insertion of the TA protein. Recently we have determined the yeast Get3 crystal structure in the open conformation. The structure suggested that Get3 may adopt an open conformation in nucleotide-free state and a closed conformation in ATP-bound state. The conformational changes to switch the Get3 between the open and closed conformations may facilitate the membrane insertions for TA proteins. Get3 may share a similar mechanism as the ABC transporters to transfer bound ligands. Now we are requesting beam time to determine Get3 crystal structure in the closed conformation to confirm our hypothesis.