Qiu Dongru, Eisinger Vonya M, Rowen Donald W, Yu Hongwei D
Department of Biochemistry and Microbiology, Joan C. Edwards School of Medicine, Marshall University, Huntington, WV 25755-9320, USA.
Proc Natl Acad Sci U S A. 2007 May 8;104(19):8107-12. doi: 10.1073/pnas.0702660104. Epub 2007 Apr 30.
Overproduction of the exopolysaccharide alginate causes mucoid conversion in Pseudomonas aeruginosa and is a poor prognosticator in cystic fibrosis. The ECF sigma factor AlgU and its cognate anti-sigma factor MucA are two principal regulators of alginate production. Here, we report the identification of three positive regulators of alginate biosynthesis: PA4033 (designated mucE), PA3649 (designated mucP), and algW. MucE, a small protein (9.5 kDa), was identified as part of a global mariner transposon screen for new regulators of alginate production. A transposon located in its promoter caused the overexpression of MucE and mucoid conversion in P. aeruginosa strains PAO1 and PA14. Accumulation of MucE in the envelope resulted in increased AlgU activity and reduced MucA levels. Three critical amino acid residues at the C terminus of MucE (WVF) were required for mucoid conversion via two predicted proteases AlgW (DegS) and MucP (RseP/YaeL). Moreover, as in Escherichia coli, the PDZ domain of AlgW was required for signal transduction. These results suggest that AlgU is regulated similarly to E. coli sigma(E) except that the amino acid triad signals from MucE and other envelope proteins that activate AlgW are slightly different from those activating DegS.
胞外多糖藻酸盐的过量产生会导致铜绿假单胞菌发生黏液样转化，并且是囊性纤维化预后不良的一个指标。胞外功能（ECF）σ因子AlgU及其同源抗σ因子MucA是藻酸盐产生的两个主要调节因子。在此，我们报告了藻酸盐生物合成的三个正向调节因子的鉴定：PA4033（命名为mucE）、PA3649（命名为mucP）和algW。MucE是一种小蛋白（9.5 kDa），是在针对藻酸盐产生新调节因子的全球水手转座子筛选中被鉴定出来的。位于其启动子中的一个转座子导致了MucE在铜绿假单胞菌菌株PAO1和PA14中的过表达以及黏液样转化。MucE在细胞膜中的积累导致AlgU活性增加和MucA水平降低。MucE C末端的三个关键氨基酸残基（WVF）通过两种预测的蛋白酶AlgW（DegS）和MucP（RseP/YaeL）对于黏液样转化是必需的。此外，与在大肠杆菌中一样，AlgW的PDZ结构域对于信号转导是必需的。这些结果表明，AlgU的调节与大肠杆菌的σE类似，只是来自MucE和其他激活AlgW的细胞膜蛋白的氨基酸三联体信号与激活DegS的信号略有不同。
