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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Solution structure and dynamics of the outer membrane enzyme PagP by NMR
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Solution structure and dynamics of the outer membrane enzyme PagP by NMR

机译：核糖核酸外膜酶PagP的溶液结构和动力学

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摘要

The bacterial outer membrane enzyme PagP transfers a palmitate chain from a phospholipid to lipid A. In a number of pathogenic Gram-negative bacteria, PagP confers resistance to certain cationic antimicrobial peptides produced during the host innate immune response. The global fold of Escherichia coli PagP was determined in both dodecylphosphocholine and n-octyl-β-D-glucoside detergent micelles using solution NMR spectroscopy. PagP consists of an eight-stranded anti-parallel β-barrel preceded by an amphipathic a helix. The β-barrel is well defined, whereas NMR relaxation measurements reveal considerable mobility in the loops connecting individual β-strands. Three amino acid residues critical for enzymatic activity localize to extracellular loops near the membrane interface, positioning them optimally to interact with the polar headgroups of lipid A. Hence, the active site of PagP is situated on the outer surface of the outer membrane. Because the phospho-lipids that donate palmitate in the enzymatic reaction are normally found only in the inner leaflet of the outer membrane, PagP activity may depend on the aberrant migration of phospholipids into the outer leaflet. This finding is consistent with an emerging paradigm for outer membrane enzymes in providing an adaptive response toward disturbances in the outer membrane.
机译：细菌外膜酶PagP将棕榈酸酯链从磷脂转移到脂质A。在许多致病性革兰氏阴性细菌中，PagP赋予对宿主固有免疫反应期间产生的某些阳离子抗菌肽的抗性。使用溶液NMR光谱法测定十二烷基磷酸胆碱和正辛基-β-D-葡萄糖苷去污剂胶束中大肠杆菌PagP的整体折叠倍数。 PagP由八链反平行β-桶组成，其后是两亲性螺旋。 β桶的定义很明确，而NMR弛豫测量显示连接各个β链的环中具有相当大的迁移率。对酶活性至关重要的三个氨基酸残基位于膜界面附近的细胞外环上，使其处于最佳位置以与脂质A的极性头基相互作用。因此，PagP的活性位点位于外膜的外表面。因为在酶促反应中贡献棕榈酸酯的磷脂通常仅在外膜的内小叶中发现，所以PagP活性可能取决于磷脂向外小叶的异常迁移。这一发现与外膜酶的新兴范式相一致，即提供对外膜干扰的适应性反应。

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