de Sousa Borges Anabela, de Keyzer Jeanine, Driessen Arnold J M, Scheffers Dirk-Jan
Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute and Zernike Institute for Advanced Materials, University of Groningen, Groningen, The Netherlands.
Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute and Zernike Institute for Advanced Materials, University of Groningen, Groningen, The Netherlands
J Bacteriol. 2015 Apr;197(8):1444-50. doi: 10.1128/JB.02556-14. Epub 2015 Feb 9.
Membrane proteins need to be properly inserted and folded in the membrane in order to perform a range of activities that are essential for the survival of bacteria. The Sec translocon and the YidC insertase are responsible for the insertion of the majority of proteins into the cytoplasmic membrane. YidC can act in combination with the Sec translocon in the insertion and folding of membrane proteins. However, YidC also functions as an insertase independently of the Sec translocon for so-called YidC-only substrates. In addition, YidC can act as a foldase and promote the proper assembly of membrane protein complexes. Here, we investigate the effect of Escherichia coli YidC depletion on the assembly of penicillin binding proteins (PBPs), which are involved in cell wall synthesis. YidC depletion does not affect the total amount of the specific cell division PBP3 (FtsI) in the membrane, but the amount of active PBP3, as assessed by substrate binding, is reduced 2-fold. A similar reduction in the amount of active PBP2 was observed, while the levels of active PBP1A/1B and PBP5 were essentially similar. PBP1B and PBP3 disappeared from higher-Mw bands upon YidC depletion, indicating that YidC might play a role in PBP complex formation. Taken together, our results suggest that the foldase activity of YidC can extend to the periplasmic domains of membrane proteins.
This study addresses the role of the membrane protein insertase YidC in the biogenesis of penicillin binding proteins (PBPs). PBPs are proteins containing one transmembrane segment and a large periplasmic or extracellular domain, which are involved in peptidoglycan synthesis. We observe that in the absence of YidC, two critical PBPs are not correctly folded even though the total amount of protein in the membrane is not affected. Our findings extend the function of YidC as a foldase for membrane protein (complexes) to periplasmic domains of membrane proteins.
膜蛋白需要在膜中正确插入并折叠，以便执行一系列对细菌生存至关重要的活动。Sec转运体和YidC插入酶负责将大多数蛋白质插入细胞质膜。YidC可与Sec转运体协同作用，参与膜蛋白的插入和折叠。然而，对于所谓的仅依赖YidC的底物，YidC也可独立于Sec转运体发挥插入酶的功能。此外，YidC可作为折叠酶，促进膜蛋白复合物的正确组装。在此，我们研究了大肠杆菌YidC缺失对参与细胞壁合成的青霉素结合蛋白（PBP）组装的影响。YidC缺失不影响膜中特定细胞分裂PBP3（FtsI）的总量，但通过底物结合评估，活性PBP3的量减少了2倍。观察到活性PBP2的量也有类似减少，而活性PBP1A/1B和PBP5的水平基本相似。YidC缺失后，PBP1B和PBP3从高分子量条带中消失，表明YidC可能在PBP复合物形成中起作用。综上所述，我们的结果表明YidC的折叠酶活性可延伸至膜蛋白的周质结构域。
本研究探讨了膜蛋白插入酶YidC在青霉素结合蛋白（PBP）生物合成中的作用。PBP是含有一个跨膜区段和一个大的周质或细胞外结构域的蛋白质，参与肽聚糖合成。我们观察到，在没有YidC的情况下，尽管膜中蛋白质的总量不受影响，但两种关键的PBP并未正确折叠。我们的发现将YidC作为膜蛋白（复合物）折叠酶的功能扩展到了膜蛋白的周质结构域。
