Vollmer W, Tomasz A
Laboratory of Microbiology, The Rockefeller University, New York, NY 10021, USA.
Mol Microbiol. 2001 Mar;39(6):1610-22. doi: 10.1046/j.1365-2958.2001.02349.x.
Streptococcus pneumoniae is a major human pathogen and many interactions of this bacterium with its host appear to be mediated, directly or indirectly, by components of the bacterial cell wall, specifically by the phosphorylcholine residues which serve as anchors for surface-located choline-binding proteins and are also recognized by components of the host response, such as the human C-reactive protein, a class of myeloma proteins and PAF receptors. In the present study, we describe the identification of the pneumococcal pce gene encoding for a teichoic acid phosphorylcholine esterase (Pce), an enzymatic activity capable of removing phosphorylcholine residues from the cell wall teichoic acid and lipoteichoic acid. Pce carries an N-terminal signal sequence, contains a C-terminal choline-binding domain with 10 homologous repeating units similar to those found in other pneumococcal surface proteins, and the catalytic (phosphorylcholine esterase) activity is localized on the N-terminal part of the protein. The mature protein was overexpressed in Escherichia coli and purified in a one-step procedure by choline-affinity chromatography and the enzymatic activity was followed using the chromophoric p-nitrophenyl-phosphorylcholine as a model substrate. The product of the enzymatic digestion of 3H-choline-labelled cell walls was shown to be phosphorylcholine. Inactivation of the pce gene in S. pneumoniae strains by insertion-duplication mutagenesis caused a unique change in colony morphology and a striking increase in virulence in the intraperitoneal mouse model. Pce may be a regulatory element involved with the interaction of S. pneumoniae with its human host.
肺炎链球菌是一种主要的人类病原体，该细菌与其宿主的许多相互作用似乎直接或间接地由细菌细胞壁的成分介导，特别是由磷酰胆碱残基介导，这些残基作为表面定位的胆碱结合蛋白的锚定物，并且也被宿主反应的成分识别，例如人类C反应蛋白、一类骨髓瘤蛋白和血小板活化因子受体。在本研究中，我们描述了肺炎球菌pce基因的鉴定，该基因编码一种磷壁酸磷酰胆碱酯酶（Pce），这是一种能够从细胞壁磷壁酸和脂磷壁酸中去除磷酰胆碱残基的酶活性。Pce带有一个N端信号序列，包含一个C端胆碱结合结构域，具有10个同源重复单元，类似于在其他肺炎球菌表面蛋白中发现的重复单元，并且催化（磷酰胆碱酯酶）活性定位于该蛋白的N端部分。成熟蛋白在大肠杆菌中过表达，并通过胆碱亲和层析一步纯化，使用发色对硝基苯基磷酰胆碱作为模型底物跟踪酶活性。3H-胆碱标记的细胞壁酶消化产物显示为磷酰胆碱。通过插入-重复诱变使肺炎链球菌菌株中的pce基因失活，导致菌落形态发生独特变化，并在腹腔小鼠模型中毒力显著增加。Pce可能是参与肺炎链球菌与其人类宿主相互作用的调节元件。
