Moehle Kerstin, Kocherla Harsha, Bacsa Bernadett, Jurt Simon, Zerbe Katja, Robinson John A, Zerbe Oliver
Department of Chemistry, University of Zurich , Winterthurerstrasse 190, CH-8057 Zürich, Switzerland.
Biochemistry. 2016 May 31;55(21):2936-43. doi: 10.1021/acs.biochem.6b00313. Epub 2016 May 19.
LptE is an outer membrane (OM) lipoprotein found in Gram-negative bacteria, where it forms a complex with the β-barrel lipopolysaccharide (LPS) transporter LptD. The LptD/E complex plays a key role in OM biogenesis, by translocating newly synthesized LPS molecules from the periplasm into the external leaflet of the asymmetric OM during cell growth. The LptD/E complex in Pseudomonas aeruginosa (Pa) is a target for macrocyclic β-hairpin-shaped peptidomimetic antibiotics, which inhibit the transport of LPS to the cell surface. So far, the three-dimensional structure of the Pa LptD/E complex and the mode of interaction with these antibiotics are unknown. Here, we report the solution structure of a Pa LptE derivative lacking the N-terminal lipid membrane anchor, determined by multidimensional solution nuclear magnetic resonance (NMR) spectroscopy. The structure reveals a central five-stranded β-sheet against which pack a long C-terminal and a short N-terminal α-helix, as found in homologues of LptE from other Gram-negative bacteria. One unique feature is an extended C-terminal helix in Pa LptE, which in a model of the Pa LptD/E complex appears to be long enough to contact the periplasmic domain of LptD. Chemical shift mapping experiments suggest only weak interactions occur between LptE and the oligosaccharide chains of LPS. The NMR structure of Pa LptE will be valuable for more detailed structural studies of the LptD/E complex from P. aeruginosa.
LptE是一种存在于革兰氏阴性菌中的外膜脂蛋白，在其中它与β桶状脂多糖（LPS）转运蛋白LptD形成复合物。LptD/E复合物在细胞生长过程中，通过将新合成的LPS分子从周质转运到不对称外膜的外小叶，在外膜生物合成中起关键作用。铜绿假单胞菌（Pa）中的LptD/E复合物是大环β发夹状拟肽抗生素的作用靶点，这类抗生素会抑制LPS向细胞表面的转运。到目前为止，Pa LptD/E复合物的三维结构以及与这些抗生素的相互作用模式尚不清楚。在此，我们报道了一种缺乏N端脂质膜锚定的Pa LptE衍生物的溶液结构，该结构通过多维溶液核磁共振（NMR）光谱法测定。该结构揭示了一个中心的五链β折叠，其两侧堆积着一个长的C端和一个短的N端α螺旋，这与其他革兰氏阴性菌中LptE的同源物情况相同。一个独特的特征是Pa LptE中有一个延伸的C端螺旋，在Pa LptD/E复合物模型中，它似乎足够长，可以与LptD的周质结构域接触。化学位移映射实验表明，LptE与LPS的寡糖链之间仅发生微弱的相互作用。Pa LptE的NMR结构对于对铜绿假单胞菌LptD/E复合物进行更详细的结构研究将具有重要价值。
