PehN, a Polygalacturonase Homologue with a Low Hydrolase Activity, Is Coregulated with the Other Erwinia chrysanthemi Polygalacturonases
PehN, a Polygalacturonase Homologue with a Low Hydrolase Activity, Is Coregulated with the Other Erwinia chrysanthemi Polygalacturonases
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PehN 是一种具有低水解酶活性的多聚半乳糖醛酸酶同源物，与其他菊欧文氏菌多聚半乳糖醛酸酶共同调控
DOI：
10.1128/jb.184.10.2664-2673.2002
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发表时间：
2002
影响因子：
3.2
通讯作者：
W. Nasser
中科院分区：
文献类型：
--
作者：
N. Hugouvieux;V. Shevchik;W. Nasser
摘要菊花欧文氏菌3937分泌大量的果胶裂解酶，其中至少有8种由PEL基因编码的果胶内切酶，它们在该细菌引起的多种植物软腐病中起主要作用。菊花还会产生一些分解果胶的水解酶。编码外聚-α-d-半乳糖醛酸苷酶的三个相邻的水解酶基因pehV、pehW和pehX已被鉴定。这些酶从果胶的非还原末端释放出双半乳糖醛酸苷。我们报告了一个新的基因，命名为pehn，编码一个与28家族的糖基水解酶同源的蛋白质，主要包括多聚半乳糖醛酸酶。PEHN对聚半乳糖醛酸酯和各种果胶具有较低的水解酶活性。PEHN作用有利于分泌的内果胶裂解酶，主要是PELB和PELC，以及周质外果胶裂解酶PELX的活性。然而，去除pehn基因并不会显著改变菊花杆菌的毒力。通过基因融合分析了PEHN转录的调控。像其他果胶酶基因一样，pehn转录依赖于几个环境条件。它是由果胶分解代谢产物诱导的，受生长期、分解代谢抑制、渗透压、厌氧、氮饥饿和钙离子存在的影响。PEHN的转录受抑制因子KdgR和环状AMP受体蛋白(CRP)的调控，KdgR控制果胶分解代谢的几乎所有步骤，而cAMP受体蛋白是糖分解代谢的全局激活剂。调节因子PECS抑制PEL基因的转录，但激活pehV、pehW和pehX基因的转录，也激活pehn的转录。三种调节因子KdgR、PECS和CRP通过直接与PEHN启动子区域相互作用发挥作用。这三个调节子和RNA聚合酶的结合所涉及的序列已经被精确定义。对这些蛋白同时结合的分析表明，CRP和RNA聚合酶是协同结合的，KdgR的结合可以阻止pehn转录。相反，PECS的激活作用与与KdgR的竞争或与CRP或RNA聚合酶的合作无关。这种效应可能是由于PECs和参与PEH调节的一种未知抑制物之间的竞争所致。
ABSTRACT Erwinia chrysanthemi 3937 secretes an arsenal of pectinolytic enzymes, including at least eight endo-pectate lyases encoded by pel genes, which play a major role in the soft-rot disease caused by this bacterium on various plants. E. chrysanthemi also produces some hydrolases that cleave pectin. Three adjacent hydrolase genes, pehV, pehW, and pehX, encoding exo-poly-α-d-galacturonosidases, have been characterized. These enzymes liberate digalacturonides from the nonreducing end of pectin. We report the identification of a novel gene, named pehN, encoding a protein homologous to the glycosyl hydrolases of family 28, which includes mainly polygalacturonases. PehN has a low hydrolase activity on polygalacturonate and on various pectins. PehN action favors the activity of the secreted endo-pectate lyases, mainly PelB and PelC, and that of the periplasmic exo-pectate lyase PelX. However, removal of the pehN gene does not significantly alter the virulence of E. chrysanthemi. Regulation of pehN transcription was analyzed by using gene fusions. Like other pectinase genes, pehN transcription is dependent on several environmental conditions. It is induced by pectic catabolic products and is affected by growth phase, catabolite repression, osmolarity, anaerobiosis, nitrogen starvation, and the presence of calcium ions. The transcription of pehN is modulated by the repressor KdgR, which controls almost all the steps of pectin catabolism, and by cyclic AMP receptor protein (CRP), the global activator of sugar catabolism. The regulator PecS, which represses the transcription of the pel genes but activates that of pehV, pehW, and pehX, also activates transcription of pehN. The three regulators KdgR, PecS, and CRP act by direct interaction with the pehN promoter region. The sequences involved in the binding of these three regulators and of RNA polymerase have been precisely defined. Analysis of the simultaneous binding of these proteins indicates that CRP and RNA polymerase bind cooperatively and that the binding of KdgR could prevent pehN transcription. In contrast, the activator effect of PecS is not linked to competition with KdgR or to cooperation with CRP or RNA polymerase. This effect probably results from competition between PecS and an unidentified repressor involved in peh regulation.
大肠杆菌二维凝胶中周质蛋白的复性和鉴定。
DOI：
--
发表时间：
1982
期刊：
The Journal of biological chemistry
影响因子：
--
作者：
Copeland,BR;Richter,RJ;Furlong,CE
通讯作者：
Furlong,CE
DOI：
10.1073/pnas.82.4.1074
发表时间：
1985-01-01
影响因子：
11.1
作者：
TABOR, S;RICHARDSON, CC
通讯作者：
RICHARDSON, CC