Gatzeva-Topalova Petia Z, Walton Troy A, Sousa Marcelo C
Department of Chemistry and Biochemistry, University of Colorado at Boulder, Boulder, CO 80309, USA.
Structure. 2008 Dec 10;16(12):1873-81. doi: 10.1016/j.str.2008.09.014.
The envelope of Gram-negative bacteria consists of inner and outer membranes surrounding the peptidoglycan wall. The outer membrane (OM) is rich in integral membrane proteins (OMPs), which have a characteristic beta barrel domain embedded in the OM. The Omp85 family of proteins, ubiquitous among Gram-negative bacteria and also present in chloroplasts and mitochondria, is required for folding and insertion of OMPs into the outer membrane. Bacterial Omp85 proteins are characterized by a periplasmic domain containing five repeats of polypeptide transport-associated (POTRA) motifs. Here we report the crystal structure of a periplasmic fragment of YaeT (the Escherichia coli Omp85) containing the first four POTRA domains in an extended conformation consistent with recent solution X-ray scattering data. Analysis of the YaeT structure reveals conformational flexibility around a hinge point between POTRA2 and 3 domains. The structure's implications for substrate binding and folding mechanisms are also discussed.
革兰氏阴性菌的包膜由围绕肽聚糖壁的内膜和外膜组成。外膜（OM）富含整合膜蛋白（OMPs），这些蛋白具有嵌入外膜的特征性β桶结构域。Omp85蛋白家族在革兰氏阴性菌中普遍存在，在叶绿体和线粒体中也有，它是OMPs折叠并插入外膜所必需的。细菌Omp85蛋白的特征是含有五个重复的多肽转运相关（POTRA）基序的周质结构域。在此，我们报道了YaeT（大肠杆菌Omp85）周质片段的晶体结构，该片段包含前四个POTRA结构域，其伸展构象与最近的溶液X射线散射数据一致。对YaeT结构的分析揭示了POTRA2和3结构域之间铰链点周围的构象灵活性。还讨论了该结构对底物结合和折叠机制的影响。
