Hugouvieux-Cotte-Pattat N, Robert-Baudouy J
Laboratoire de Microbiologie, Institut National des Sciences Appliquées, Villeurbanne, France.
Mol Microbiol. 1989 Nov;3(11):1587-97. doi: 10.1111/j.1365-2958.1989.tb00144.x.
Various mutations in the pectin catabolic pathway of Erwinia chrysanthemi were isolated by selection of Mu-lac insertions, resulting in expression of the lac genes inducible by pectin degradation products. This approach allowed us to isolate lacZ fusions with the genes pelC, pelD, ogl and pem, encoding pectate lyases PLc and PLd, oligogalacturonate lyase and pectin methylesterase, respectively. Moreover, we obtained mutations affecting the regulation of pectinolytic enzymes; a locus called pecl appeared to be involved in induction of pectate lyases and pectin methylesterase. A second locus, called pecL, may encode an activator protein acting on pectate lyase production. Both pecl and pecL expression are induced in the presence of pectic polymers. The expression of the pem gene was studied in more detail by analysis of the pem-lacZ fusions. The expression of pem appears to be controlled by the negative regulatory gene kdgR, which controls all the genes involved in pectin degradation (pem, pel, ogl, kduD, kdul, kdgK, kdgA). This study confirmed that 2-keto-3-deoxygluconate is a key intermediate for the induction of the pectin catabolic pathway. The three genes pem, pelD and pecl were localized in the same region, near the ade-377 marker on the genetic map of the E. chrysanthemi strain 3937. The pem gene was located more precisely on an 18kb DNA fragment containing the pelADE cluster. However, this 18kb DNA fragment did not complement the pecl mutation. The pecL mutations were located near the ile-2 marker on the genetic map of E. chrysanthemi strain 3937.
通过选择Mu - lac插入，分离出了菊欧文氏菌果胶分解代谢途径中的各种突变体，从而使lac基因能够被果胶降解产物诱导表达。这种方法使我们能够分离出与pelC、pelD、ogl和pem基因的lacZ融合体，这些基因分别编码果胶酸裂解酶PLc和PLd、寡聚半乳糖醛酸裂解酶和果胶甲基酯酶。此外，我们还获得了影响果胶分解酶调控的突变；一个名为pecl的位点似乎参与了果胶酸裂解酶和果胶甲基酯酶的诱导。另一个位点，称为pecL，可能编码一种作用于果胶酸裂解酶产生的激活蛋白。pecl和pecL的表达在果胶聚合物存在时被诱导。通过对pem - lacZ融合体的分析，对pem基因的表达进行了更详细的研究。pem的表达似乎受负调控基因kdgR控制，kdgR控制所有参与果胶降解的基因（pem、pel、ogl、kduD、kdul、kdgK、kdgA）。这项研究证实2 - 酮 - 3 - 脱氧葡萄糖酸是果胶分解代谢途径诱导的关键中间产物。pem、pelD和pecl这三个基因位于同一区域，靠近菊欧文氏菌3937菌株遗传图谱上的ade - 377标记。pem基因更精确地定位在一个包含pelADE簇的18kb DNA片段上。然而，这个18kb DNA片段不能互补pecl突变。pecL突变位于菊欧文氏菌3937菌株遗传图谱上ile - 2标记附近。
