Outer-membrane lipoprotein LpoB spans the periplasm to stimulate the peptidoglycan synthase PBP1B
Outer-membrane lipoprotein LpoB spans the periplasm to stimulate the peptidoglycan synthase PBP1B
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DOI：
10.1073/pnas.1400376111
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发表时间：
2014-06-03
影响因子：
11.1
通讯作者：
Simorre, Jean-Pierre
中科院分区：
文献类型：
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作者：
Egan, Alexander J. F.;Jean, Nicolas L.;Simorre, Jean-Pierre
细菌的细胞质膜周围有一层重要的、承受压力的肽聚糖（PG）层。生长和分裂的细胞通过使用膜锚定的PG激酶来扩展其PG层，所述膜锚定的PG激酶由动态细胞骨架元件引导。在大肠杆菌中，主要单层PG的生长也受到外膜锚定脂蛋白的调节。脂蛋白LpoB是激活青霉素结合蛋白（PBP）1B所必需的，PBP 1B是一种主要的双功能PG合酶，具有聚糖链聚合（糖基转移酶）和肽交联（转肽酶）活性。在这里，我们报告的LpoB的结构，确定通过NMR光谱，显示一个N-末端，54-aa-长的灵活的拉伸，然后由一个球状域的N-末端结构域的流行周质蛋白TolB的相似性。我们已经确定了LpoB的球状结构域和PBP 1B的非催化UvrB结构域2同源结构域之间的相互作用界面，并对复合物进行了建模。该界面内的氨基酸交换减弱PBP 1B-LpoB相互作用，降低PBP 1B体外刺激，并损害其体内功能。相反，LpoB的N-末端柔性伸展需要在体内刺激PBP 1B，但在体外被抑制。这支持了LpoB跨越周质与PBP 1B相互作用并刺激PG合成的模型。
Bacteria surround their cytoplasmic membrane with an essential, stress-bearing peptidoglycan (PG) layer. Growing and dividing cells expand their PG layer by using membrane-anchored PG synthases, which are guided by dynamic cytoskeletal elements. In Escherichia coli, growth of the mainly single-layered PG is also regulated by outer membrane-anchored lipoproteins. The lipoprotein LpoB is required for the activation of penicillin-binding protein (PBP) 1B, which is a major, bifunctional PG synthase with glycan chain polymerizing (glycosyltransferase) and peptide cross-linking (transpeptidase) activities. Here, we report the structure of LpoB, determined by NMR spectroscopy, showing an N-terminal, 54-aa-long flexible stretch followed by a globular domain with similarity to the N-terminal domain of the prevalent periplasmic protein TolB. We have identified the interaction interface between the globular domain of LpoB and the noncatalytic UvrB domain 2 homolog domain of PBP1B and modeled the complex. Amino acid exchanges within this interface weaken the PBP1B-LpoB interaction, decrease the PBP1B stimulation in vitro, and impair its function in vivo. On the contrary, the N-terminal flexible stretch of LpoB is required to stimulate PBP1B in vivo, but is dispensable in vitro. This supports a model in which LpoB spans the periplasm to interact with PBP1B and stimulate PG synthesis.