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首页> 外文期刊>Biochemistry >Association of spin-labeled lipids with beta-barrel proteins from the outer membrane of Escherichia coli
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Association of spin-labeled lipids with beta-barrel proteins from the outer membrane of Escherichia coli

机译：旋转标记的脂质与大肠杆菌外膜中的β-桶蛋白的关联

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摘要

The interaction of spin-labeled lipids with beta-barrel transmembrane proteins has been studied by the electron spin resonance (ESR) methods developed for alpha-helical integral proteins. The outer membrane protein OmpA and the ferrichrome-iron receptor FhuA from the outer membrane of Escherichia coli were reconstituted in bilayers of dimyristoylphosphatidylglycerol. The ESR spectra from phosphatidylglycerol spin labeled on the 14-C atom of the sn-2 chain contain a second component from motionally restricted lipids contacting the intramembranous surface of the beta-barrel, in addition to that from the fluid bilayer lipids. The stoichiometry of motionally restricted lipids, 11 and 32 lipids/monomer for OmpA and FhuA, respectively, is constant irrespective of the total lipid/protein ratio. It is proportional to the number of transmembrane beta-strands, eight for OmpA and 22 for FhuA, and correlates reasonably well with the intramembranous perimeter of the protein. Spin-labeled lipids with different polar headgroups display a differential selectivity of interaction with the two proteins. The more pronounced pattern of lipid selectivity for FhuA than for OmpA correlates with the preponderance of positively charged residues facing the lipids in the extensions of the beta-sheet and shorter interconnecting loops on the extracellular side of FhuA.
机译：旋转标记的脂质与β-桶形跨膜蛋白的相互作用已通过为α-螺旋整合蛋白开发的电子自旋共振（ESR）方法进行了研究。将来自大肠杆菌外膜的外膜蛋白OmpA和亚铁铬铁受体FhuA重构为二豆香油基磷脂酰甘油的双层膜。在sn-2链的14-C原子上自旋标记的磷脂酰甘油的ESR谱图除了包含流体双层脂质的光谱外，还包含与β-桶的膜内表面接触的受运动限制的脂质的第二种成分。受运动限制的脂质（分别为OmpA和FhuA的11和32个脂质/单体）的化学计量是恒定的，而与总脂质/蛋白质之比无关。它与跨膜β链的数量成正比，OmpA为八个，FhuA为22，并且与蛋白质的膜内周长合理相关。具有不同极性头基的自旋标记脂质显示出与两种蛋白质相互作用的选择性差异。对FhuA的脂类选择性比对OmpA的脂类选择性模式更为明显，这与在β-sheet延伸区和FhuA胞外侧较短的互连环上面对脂质的带正电荷的残基占优势有关。

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