Structural basis for heme detoxification by an ATP-binding cassette-type efflux pump in gram-positive pathogenic bacteria.
Structural basis for heme detoxification by an ATP-binding cassette-type efflux pump in gram-positive pathogenic bacteria.
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DOI：
10.1073/pnas.2123385119
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发表时间：
2022-07-05
影响因子：
11.1
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中科院分区：
文献类型：
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血红素（铁-原卟啉IX复合物）在过量时具有极强的细胞毒性，尽管它在许多生物过程中起着重要作用。由于其亲脂性，游离血红素集中在脂质膜中，产生有害的活性氧。病原菌通过降解、螯合和挤出来克服血红素的毒性，同时它们将来自宿主含血红素蛋白的血红素同化为铁营养物。为了消除血红素毒性，白喉棒状杆菌和许多革兰氏阳性细菌在其细胞质膜中具有血红素专用外排泵HrtBA。我们的功能和结构数据揭示了HrtBA如何使用ATP从膜中排出血红素，阐明了宿主血液中细菌血红素解毒的机制。细菌病原体从宿主血红蛋白获得血红素作为铁营养素，用于其毒性和在血液中的增殖。同时，他们遇到的无细胞毒性血红素逃脱血红素收购过程。为了克服这种毒性，许多革兰氏阳性细菌在细胞质膜中采用ATP结合盒血红素专用外排泵HrtBA。虽然遗传分析表明，HrtBA驱逐血红素从细菌膜，血红素流出的分子机制仍然难以捉摸，由于缺乏蛋白质的研究。在这里，我们展示了白喉棒状杆菌HrtBA的生化特性和晶体结构，单独和与血红素或ATP类似物的复合物，我们揭示了HrtBA如何从膜中提取血红素并释放它。HrtBA由两个细胞质HrtA ATP酶亚基和两个跨膜HrtB通透酶亚基组成。血红素结合位点在HrtB二聚体中形成，并且在膜的外小叶中可侧向接近血红素。血红素结合位点使用任一亚基的谷氨酸残基作为轴向配体从膜捕获血红素，并将血红素隔离在重排的跨膜螺旋束内。通过ATP驱动的HrtA二聚化，血红素结合位点被挤压以挤出结合的血红素。该机制揭示了这种细菌中膜结合血红素的解毒作用。
Heme (iron-protoporphyrin IX complex) is extremely cytotoxic when in excess, although it plays an important role in numerous biological processes. Due to its lipophilicity, free heme is concentrated in lipid membranes, generating harmful reactive oxygen species. Pathogenic bacteria overcome heme toxicity via degradation, sequestration, and extrusion, while they assimilate heme derived from the host heme-containing proteins as an iron nutrient. To eliminate heme toxicity, Corynebacterium diphtheriae and many gram-positive bacteria possess a heme-dedicated efflux pump, HrtBA, in their cytoplasmic membranes. Our functional and structural data reveal how HrtBA expels heme from the membrane using ATP, elucidating a mechanism of bacterial heme detoxification in host blood. Bacterial pathogens acquire heme from the host hemoglobin as an iron nutrient for their virulence and proliferation in blood. Concurrently, they encounter cytotoxic-free heme that escapes the heme-acquisition process. To overcome this toxicity, many gram-positive bacteria employ an ATP-binding cassette heme-dedicated efflux pump, HrtBA in the cytoplasmic membranes. Although genetic analyses have suggested that HrtBA expels heme from the bacterial membranes, the molecular mechanism of heme efflux remains elusive due to the lack of protein studies. Here, we show the biochemical properties and crystal structures of Corynebacterium diphtheriae HrtBA, alone and in complex with heme or an ATP analog, and we reveal how HrtBA extracts heme from the membrane and releases it. HrtBA consists of two cytoplasmic HrtA ATPase subunits and two transmembrane HrtB permease subunits. A heme-binding site is formed in the HrtB dimer and is laterally accessible to heme in the outer leaflet of the membrane. The heme-binding site captures heme from the membrane using a glutamate residue of either subunit as an axial ligand and sequesters the heme within the rearranged transmembrane helix bundle. By ATP-driven HrtA dimerization, the heme-binding site is squeezed to extrude the bound heme. The mechanism sheds light on the detoxification of membrane-bound heme in this bacterium.
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影响因子：
28.3
作者：
Fitzpatrick AWP;Llabrés S;Neuberger A;Blaza JN;Bai XC;Okada U;Murakami S;van Veen HW;Zachariae U;Scheres SHW;Luisi BF;Du D
通讯作者：
Du D
影响因子：
6.7
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Friedman DB;Stauff DL;Pishchany G;Whitwell CW;Torres VJ;Skaar EP
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2.9
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影响因子：
3.6
作者：
Joubert, Laetitia;Derre-Bobillot, Aurelie;Lechardeur, Delphine
通讯作者：
Lechardeur, Delphine
影响因子：
5.2
作者：
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通讯作者：
Koronakis V