Role of an alginate lyase for alginate transport in mucoid Pseudomonas aeruginosa
Role of an alginate lyase for alginate transport in mucoid Pseudomonas aeruginosa
复制标题
DOI：
10.1128/iai.73.10.6429-6436.2005
复制
发表时间：
2005-10-01
影响因子：
3.1
通讯作者：
Ohman, DE
中科院分区：
文献类型：
--
作者：
Jain, S;Ohman, DE
条件致病菌铜绿假单胞菌分泌一种称为藻酸盐的胶囊状多糖，其对于逃避宿主防御非常重要，特别是在囊性纤维化（CF）患者的慢性肺病期间。大多数用于藻酸盐生物合成的蛋白质由12基因algD操纵子编码。有趣的是，该操纵子还编码AlgL，一种降解藻酸盐的裂解酶。缺乏AlgG、AlgK或AlgX的突变体（也由操纵子编码）合成藻酸盐聚合物，这些聚合物被共调节蛋白AlgL消化。我们研究了高度粘液样CF分离株FRD 1中Delta algL突变的表型。只有当algD操纵子在LacI（q）抑制的trc启动子的控制下时，才可能产生真正的Delta algL突变体。在用异丙基-β-D-硫代吡喃半乳糖苷诱导藻酸盐产生后，Delta algL突变体细胞在几小时内裂解。Delta algL突变体的电子显微照片显示藻酸盐聚合物在周质中积累，最终使细菌细胞壁破裂。在藻酸盐过量生产菌株中对AlgL的需求导致了一种新的藻酸盐分泌模型，其中多蛋白分泌复合物（或支架，其包括AlgG、AlgK、AlgX和AlgL）引导新的聚合物通过周质以跨外膜分泌。在该模型中，AlgL是双功能的，具有在支架中的结构作用和在降解周质中的游离藻酸盐聚合物中的作用。
The opportunistic pathogen Pseudomonas aeruginosa secretes a capsule-like polysaccharide called alginate that is important for evasion of host defenses, especially during chronic pulmonary disease of patients with cystic fibrosis (CF). Most proteins for alginate biosynthesis are encoded by the 12-gene algD operon. Interestingly, this operon also encodes AlgL, a lyase that degrades alginate. Mutants lacking AlgG, AlgK, or AlgX, also encoded by the operon, synthesize alginate polymers that are digested by the coregulated protein AlgL. We examined the phenotype of an Delta algL mutation in the highly mucoid CF isolate FRD1. Generating a true Delta algL mutant was possible only when the algD operon was under the control of a LacI(q) -repressed trc promoter. Upon induction of alginate production with isopropyl-beta-D-thiogalactopyranoside, the Delta algL mutant cells were lysed within a few hours. Electron micrographs of the Delta algL mutant showed that alginate polymers accumulated in the periplasm, which ultimately burst the bacterial cell wall. The requirement of AlgL in an alginate-overproducing strain led to a new model for alginate secretion in which a multiprotein secretion complex (or scaffold, that includes AlgG, AlgK, AlgX, and AlgL) guides new polymers through the periplasm for secretion across the outer membrane. In this model, AlgL is bifunctional with a structural role in the scaffold and a role in degrading free alginate polymers in the periplasm.