Centre for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, Stockholm SE-106 91, Sweden.
Protein Sci. 2011 Sep;20(9):1520-9. doi: 10.1002/pro.677. Epub 2011 Jul 13.
Penicillin-binding protein 5 (PBP5) is a DD-carboxypeptidase, which cleaves the terminal D-alanine from the muramyl pentapeptide in the peptidoglycan layer of Escherichia coli and other bacteria. In doing so, it varies the substrates for transpeptidation and plays a key role in maintaining cell shape. In this study, we have analyzed the oligomeric state of PBP5 in detergent and in its native environment, the inner membrane. Both approaches indicate that PBP5 exists as a homo-oligomeric complex, most likely as a homo-dimer. As the crystal structure of the soluble domain of PBP5 (i.e., lacking the membrane anchor) shows a monomer, we used our experimental data to generate a model of the homo-dimer. This model extends our understanding of PBP5 function as it suggests how PBP5 can interact with the peptidoglycan layer. It suggests that the stem domains interact and the catalytic domains have freedom to move from the position observed in the crystal structure. This would allow the catalytic domain to have access to pentapeptides at different distances from the membrane.
青霉素结合蛋白 5（PBP5）是一种 DD-羧肽酶，可将肽聚糖层中大肠杆菌和其他细菌的末端 D-丙氨酸从 muramyl 五肽中切割出来。这样，它改变了转肽酶的底物，并在维持细胞形状方面发挥着关键作用。在这项研究中，我们分析了 PBP5 在去污剂和其天然环境——内膜中的聚合状态。这两种方法都表明 PBP5 作为同型寡聚复合物存在，最有可能是同型二聚体。由于 PBP5 的可溶性结构域（即缺乏膜锚定）的晶体结构显示为单体，因此我们使用实验数据生成了同型二聚体的模型。该模型扩展了我们对 PBP5 功能的理解，因为它表明了 PBP5 如何与肽聚糖层相互作用。它表明，茎域相互作用，并且催化域可以从晶体结构中观察到的位置自由移动。这将允许催化域能够与距膜不同距离的五肽相互作用。
