K3 Projective models in scrolls
K3 Projective models in scrolls
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DOI：
10.1007/b97183
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发表时间：
2001-08
影响因子：
9.3
通讯作者：
T. Johnsen;A. L. Knutsen
中科院分区：
文献类型：
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作者：
T. Johnsen;A. L. Knutsen
蛋白质介导的溶质跨细胞膜转运是由一个大的，不同的家族的多位整合膜蛋白称为转运蛋白催化。运输机分为两类。通道的特征在于接近扩散极限的高催化通量。载体经历缓慢的、底物诱导的构象变化，导致溶质转运速率较低。信道和载波结构的最新进展强调了这一领域面临的挑战。一些转运蛋白已被结晶为单体转运蛋白。这些结构提供了对单个通道和载体功能的巨大洞察。其他转运蛋白已被结晶为有序的寡聚体，其中每个亚基呈现单独的转运途径。虽然揭示了许多关于转运蛋白功能的信息，但尚不清楚为什么这些结构会组装成低聚物。低分辨率分析表明，一些转运蛋白在脂质双层内形成低聚复合物，但可能保留低聚结构或在洗涤剂中解离成单体形式。对一个共同亚群（例如主要促进因子超家族）的大量转运蛋白的遗传和生物物理分析表明，特定蛋白质可以形成单体、二聚体、三聚体或四聚体复合物。虽然最小的MFS转运途径似乎是含有12个跨膜结构域的单体，但一些转运蛋白可能需要二聚体来催化转运。当溶质特异性可以通过重新设计一个共同的催化支架来进化时，为什么会有如此多的多样性呢？答案可能与运输监管的功能和复杂性有关。我们描述了MFS转运蛋白GluT 1-人红细胞的葡萄糖转运蛋白的寡聚体结构。我们表明，动力学的GluT 1介导的糖转运和细胞内核苷酸的调节是由转运蛋白寡聚体结构。
Protein mediated solute transport across cell membranes is catalyzed by a large, diverse family of polytopic integral membrane proteins called transporters. Transporters fall into two classes. The channels are characterized by high catalytic throughput approaching the diffusional limit. The carriers undergo slow, substrate-induced conformational changes resulting in lower rates of solute transport. Recent advances in channel and carrier structure emphasize the challenges presented to this field. Several transporters have been crystallized as monomeric transport proteins. These structures provide enormous insight into individual channel and carrier function. Other transporters have been crystallized as ordered oligomers in which each subunit presents an individual transport pathway. While revealing much about transporter function, it is unclear why these structures assemble as oligomers. Low-resolution analyses show that some transporters form oligomeric complexes within the lipid bilayer but may retain oligomeric structure or dissociate into monomeric forms in detergents. Genetic and biophysical analysis of a large number of transport proteins of a common subgroup (e.g. Major Facilitator Superfamily) indicates that specific proteins may form monomeric, dimeric, trimeric or tetrameric complexes. While the minimal MFS transport pathway appears to be a monomer containing 12 membrane-spanning domains, some transporters may require dimers to catalyze transport. Why such diversity when solute specificity could evolve by re-engineering a common catalytic scaffold? The answer may be related to function and the complexity of transport regulation. We describe the oligomeric structure of an MFS transporter GluT1 – the glucose transport protein of human red blood cells. We show that the kinetics of GluT1-mediated sugar transport and its regulation by intracellular nucleotides are determined by transporter oligomeric structure.