Two distinct loci affecting conversion to mucoidy in Pseudomonas aeruginosa in cystic fibrosis encode homologs of the serine protease HtrA
Two distinct loci affecting conversion to mucoidy in Pseudomonas aeruginosa in cystic fibrosis encode homologs of the serine protease HtrA
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DOI：
10.1128/jb.178.2.511-523.1996
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发表时间：
1996-01-01
影响因子：
3.2
通讯作者：
Deretic, V
中科院分区：
文献类型：
--
作者：
Boucher, JC;MartinezSalazar, J;Deretic, V
在铜绿假单胞菌中转化为粘液样、外泌多糖藻酸盐过量生产表型与囊性纤维化中的慢性呼吸道感染相关。粘液样是由mac突变引起的，该mac突变使替代性σ因子AlgU去抑制，其进而激活藻酸盐生物合成和辅助调节基因。在这里，我们报告的分子特征的两个新发现的基因，algW和mucD，影响表达的粘液。algW基因，映射在69分钟，分离的基础上，它的能力，以抑制粘体和减少转录的藻酸盐生物合成基因algD，预测的AlgW的一级结构显示相似的HtrA（DegP），丝氨酸蛋白酶参与异常蛋白质的蛋白水解和所需的抗氧化和热应激的肠道细菌。失活algW的染色体上的野生型nonmucoid菌株PAO1引起增加的敏感性热，H2O2，百草枯，氧化还原循环化合物诱导细胞内的超氧化物，这种突变也允许显着诱导藻酸盐的生产中存在的亚抑制浓度的百草枯。两个新的基因，mucC和mucD，被确定为紧接下游的先前表征的部分（algU mucA mucB）的基因簇在67.5分钟编码的替代西格玛因子AlgU及其监管机构。有趣的是，mucD的预测基因产物也显示出与HtrA的相似性。PAO 1染色体上mucD的失活导致向粘液样表型的转化。mucD突变体对H_2O_2和热杀菌的敏感性也增加，但与algW突变体相比，mucD突变体对百草枯的敏感性没有增加。这些发现表明algW和mucD在铜绿假单胞菌对活性氧中间体和热的抗性中发挥部分重叠但不同的作用。此外，由于mucD和algW的突变导致转化为粘液性或降低活性氧中间体对其诱导的阈值，这些因子可通过直接作用于AlgU或其调节剂或通过去除可激活这个应激反应系统
Conversion to a mucoid, exopolysaccharide alginate-overproducing phenotype in Pseudomonas aeruginosa is associated with chronic respiratory infections in cystic fibrosis, Mucoidy is caused by mac mutations that derepress the alternative sigma factor AlgU, which in turn activates alginate biosynthetic and ancillary regulatory genes. Here we report the molecular characterization of two newly identified genes, algW and mucD, that affect expression of mucoidy. The algW gene, mapping at 69 min, was isolated on the basis of its ability to suppress mucoidy and reduce transcription of the alginate biosynthetic gene algD, The predicted primary structure of AlgW displayed similarity to HtrA (DegP), a serine protease involved in proteolysis of abnormal proteins and required for resistance to oxidative and heat stress in enteric bacteria. Inactivation of algW on the chromosome of the wild-type nonmucoid strain PAO1 caused increased sensitivity to heat, H2O2, and paraquat, a redox cycling compound inducing intracellular levels of superoxide, This mutation also permitted significant induction of alginate production in the presence of subinhibitory concentrations of paraquat. Two new genes, mucC and mucD, were identified immediately downstream of the previously characterized portion (algU mucA mucB) of the gene cluster at 67.5 min encoding the alternative sigma factor AlgU and its regulators. Interestingly, the predicted gene product of mucD also showed similarities to HtrA, Inactivation of mucD on the PAO1 chromosome resulted in conversion to the mucoid phenotype. The mutation in mucD also caused increased sensitivity to H2O2 and heat killing, However, in contrast to algW mutants, no increase in susceptibility to paraquat was observed in mucD mutants. These findings indicate that algW and mucD play partially overlapping but distinct roles in P. aeruginosa resistance to reactive oxygen intermediates and heat, In addition, since mutations in mucD and algW cause conversion to mucoidy or lower the threshold for its induction by reactive oxygen intermediates, these factors may repress alginate synthesis either directly by acting on AlgU or its regulators or indirectly by removing physiological signals that may activate this stress response system.