Thurn K K, Chatterjee A K
Appl Environ Microbiol. 1985 Oct;50(4):894-8. doi: 10.1128/aem.50.4.894-898.1985.
Exponentially growing cells of Erwinia chrysanthemi EC16 usually export about 98% of their pectate lyase (PL) and protease, about 40% of their polygalacturonase (PG), and about 60% of their cellulase (endoglucanase or carboxymethyl cellulase; CL). By using the R plasmid, pJB4JI (pPH1JI::Mu::Tn5), three independent Tn5 insertion mutants were obtained that exported normal levels of protease but 10% or less of PL, PG, and CL. Physical analysis revealed that single copies of Tn5 had inserted into the E. chrysanthemi chromosome, producing a similar export-defective (Out-) phenotype. The synthesis of PL, PG, and CL was not affected by the Tn5 insertions. These enzymes were released from the mutants on spheroplast formation, indicating that they were located in the periplasmic space. Tn5 insertions caused the loss of a 35-kilodalton periplasmic protein, but did not alter the outer membrane protein composition. The findings are discussed with respect to the current knowledge on protein export in gram-negative bacteria.
菊欧文氏菌EC16的指数生长期细胞通常会分泌约98%的果胶酸裂解酶（PL）和蛋白酶、约40%的多聚半乳糖醛酸酶（PG）和约60%的纤维素酶（内切葡聚糖酶或羧甲基纤维素酶；CL）。利用R质粒pJB4JI（pPH1JI::Mu::Tn5），获得了三个独立的Tn5插入突变体，这些突变体分泌的蛋白酶水平正常，但PL、PG和CL的分泌量仅为正常水平的10%或更低。物理分析表明，单拷贝的Tn5已插入菊欧文氏菌染色体，产生了类似的分泌缺陷（Out-）表型。PL、PG和CL的合成不受Tn5插入的影响。这些酶在原生质球形成时从突变体中释放出来，表明它们位于周质空间。Tn5插入导致一种35千道尔顿的周质蛋白缺失，但未改变外膜蛋白组成。结合目前关于革兰氏阴性菌蛋白质分泌的知识对这些发现进行了讨论。
