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首页> 外文期刊>Biochemistry >Mechanism of Ferripyoverdine Uptake by Pseudomonas aeruginosa Outer Membrane Transporter FpvA: No Diffusion Channel Formed at Any Time during Ferrisiderophore Uptake
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Mechanism of Ferripyoverdine Uptake by Pseudomonas aeruginosa Outer Membrane Transporter FpvA: No Diffusion Channel Formed at Any Time during Ferrisiderophore Uptake

机译：铜绿假单胞菌外膜转运蛋白FpvA吸收Ferripyoverdine的机制：吸收铁的过程中的任何时间都没有形成扩散通道。

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To get access to iron, Pseudomonas aeruginosa produces the siderophore pyoverdine (PVD), composed of a fluorescent chromophore linked to an octapeptide, and its corresponding outer membrane transporter FpvA. This transporter is composed of three domains: a beta-barrel inserted into the membrane, a plug that closes the channel formed by the barrel, and a signaling domain in the periplasm. The plug and the signaling domain are separated by a sequence of five residues called the TonB box, which is necessary for the interaction of FpvA with the inner membrane TonB protein. Genetic deletion of the plug domain resulted in the presence of beta-barrel in the outer membrane unable to bind and transport PVD-Fe. Expression of the soluble plug domain with the TonB box inhibited PVD-Fe-55 uptake most likely through interaction with TonB in the periplasm. A reconstituted FpvA in the bacterial outer membrane was obtained by the coexpression of separately encoded plug and beta-barrel domains, each endowed with a signal sequence and a signaling domain. This resulted in polypeptide complementation after secretion across the cytoplasmic membrane. The reconstituted FpvA bound PVD-Fe with the same affinity as wild-type FpvA, indicating that the resulting transporter is correctly folded and reconstituted in the outer membrane. PVD-Fe uptake was TonB-dependent but 75% less efficient compared to wild-type FpvA. These data are consistent with a gated mechanism in which no open channel with a complete removal of the plug domain for PVD-Fe diffusion is formed in FpvA at any point during the uptake cycle.
机译：为了获得铁，铜绿假单胞菌产生了铁载体吡overdine（PVD），其由与八肽连接的荧光发色团及其相应的外膜转运蛋白FpvA组成。该转运蛋白由三个结构域组成：插入膜中的β-桶，封闭由桶形成的通道的塞子和周质中的信号传导域。塞子和信号结构域被称为TonB框的五个残基序列隔开，这对于FpvA与内膜TonB蛋白的相互作用是必需的。塞结构域的遗传缺失导致在外膜中存在无法结合和运输PVD-Fe的β-桶。用TonB盒表达可溶的塞结构域最可能通过与周质中的TonB相互作用来抑制PVD-Fe-55的摄取。通过共编码分别编码的栓结构域和β-桶状结构域获得细菌外膜中的重组FpvA，每个结构域均具有信号序列和信号传导结构域。跨细胞质膜分泌后，这导致多肽互补。重构的FpvA结合的PVD-Fe具有与野生型FpvA相同的亲和力，表明所得转运蛋白已正确折叠并重构在外膜中。 PVD-Fe的吸收依赖于TonB，但与野生型FpvA相比效率低75％。这些数据与门控机制一致，在门控机制中，在摄取周期中的任何时间点都没有在FpvA中形成完全去除用于PVD-Fe扩散的栓塞域的开放通道。

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