DpaA detaches Braun's lipoprotein from peptidoglycan
DpaA detaches Braun's lipoprotein from peptidoglycan
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DpaA 将布劳恩脂蛋白与肽聚糖分离
DOI：
10.1101/2021.02.21.432140
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
Winkle M
中科院分区：
文献类型：
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作者：
Winkle M
革兰氏阴性菌有一个独特的细胞包膜，含有脂多糖的外膜与一层薄薄的肽聚糖紧密相连。肠杆菌（如大肠杆菌）通过转肽酶LdtA、LdtB和LdtC介导，将丰富的外膜锚定脂蛋白Lpp（Braun's lipoprotein）共价结合到肽聚糖中的三肽上。LdtD和LdtE是同一个D-转肽酶家族的成员，但它们催化不同的反应，即在肽聚糖中形成3-3交联。第六个同源物在大肠杆菌中的功能。LdtF在大肠杆菌中的作用尚不清楚，尽管已显示其在具有抑制的脂多糖输出到外膜的细胞中是必需的。我们现在发现LdtF水解Lpp-肽聚糖键，将Lpp从肽聚糖上分离，并将LdtF重命名为肽聚糖内消旋-二氨基庚二酸蛋白酰胺酶A（DpaA）。我们表明，从肽聚糖LPP的分离是有益的细胞在一定的压力条件下，并删除ofdpaA允许频繁的转座子失活的thelapB（yciM）基因，其产品下调脂多糖的生物合成。DpaA样蛋白具有特征性的序列基序，存在于许多革兰氏阴性细菌中，其中一些没有Lpp，这提高了DpaA在这些物种中具有其他底物的可能性。总之，我们的数据表明，在E.重要提示革兰氏阴性菌有一个复杂的细胞被膜，有两层膜和一个含有肽聚糖层的周质。外膜通过高度丰富的蛋白质与肽聚糖牢固连接。外膜锚定的Braun脂蛋白（Lpp）是大肠杆菌中含量最丰富的蛋白质。在大肠杆菌中，大约三分之一的Lpp分子与肽聚糖中的三肽共价连接。Lpp与肽聚糖的连接稳定了细胞包膜，并且对于外膜作为一系列毒性分子和抗生素的渗透性屏障起作用至关重要。到目前为止，Lpp与肽聚糖的连接被认为是不可逆的。我们现在已经确定了一种酰胺酶，DpaA，这是能够脱离LPP的肽聚糖，我们表明，脱离LPP在一定的压力条件下是重要的。DpaA样蛋白存在于许多革兰氏阴性细菌中，并且在这些物种中可能具有不同的底物。
Gram-negative bacteria have a unique cell envelope with a lipopolysaccharide-containing outer membrane that is tightly connected to a thin layer of peptidoglycan. The tight connection between the outer membrane and peptidoglycan is needed to maintain the outer membrane as an impermeable barrier for many toxic molecules and antibiotics.Enterobacteriaceaesuch as Escherichia coli covalently attach the abundant outer membrane-anchored lipoprotein Lpp (Braun’s lipoprotein) to tripeptides in peptidoglycan, mediated by the transpeptidases LdtA, LdtB, and LdtC. LdtD and LdtE are members of the same family ofld-transpeptidases but they catalyze a different reaction, the formation of 3-3 cross-links in the peptidoglycan. The function of the sixth homologue in E. coli, LdtF, remains unclear, although it has been shown to become essential in cells with inhibited lipopolysaccharide export to the outer membrane. We now show that LdtF hydrolyzes the Lpp-peptidoglycan linkage, detaching Lpp from peptidoglycan, and have renamed LdtF to peptidoglycanmeso-diaminopimelic acidproteinamidaseA(DpaA). We show that the detachment of Lpp from peptidoglycan is beneficial for the cell under certain stress conditions and that the deletion ofdpaAallows frequent transposon inactivation in thelapB(yciM) gene, whose product downregulates lipopolysaccharide biosynthesis. DpaA-like proteins have characteristic sequence motifs and are present in many Gram-negative bacteria, of which some have no Lpp, raising the possibility that DpaA has other substrates in these species. Overall, our data show that the Lpp-peptidoglycan linkage in E. coli is more dynamic than previously appreciated.IMPORTANCEGram-negative bacteria have a complex cell envelope with two membranes and a periplasm containing the peptidoglycan layer. The outer membrane is firmly connected to the peptidoglycan by highly abundant proteins. The outer membrane-anchored Braun’s lipoprotein (Lpp) is the most abundant protein in E. coli, and about one-third of the Lpp molecules become covalently attached to tripeptides in peptidoglycan. The attachment of Lpp to peptidoglycan stabilizes the cell envelope and is crucial for the outer membrane to function as a permeability barrier for a range of toxic molecules and antibiotics. So far, the attachment of Lpp to peptidoglycan has been considered to be irreversible. We have now identified an amidase, DpaA, which is capable of detaching Lpp from peptidoglycan, and we show that the detachment of Lpp is important under certain stress conditions. DpaA-like proteins are present in many Gram-negative bacteria and may have different substrates in these species.