Li Baoguang, Brown Eric W, D'Agostino Christine, LeClerc J Eugene, Cebula Thomas A
Division of Molecular Biology, Center for Food Safety and Applied Nutrition, Food and Drug Administration, 8301 Muirkirk Road, Laurel, MD 20708, USA.
Microbiology (Reading). 2005 Aug;151(Pt 8):2671-2683. doi: 10.1099/mic.0.27990-0.
Phosphoprotein phosphatases encoded by the prpA and prpB genes function in signal transduction pathways for degradation of misfolded proteins in the extracytoplasmic compartments of Escherichia coli. In order to trace the evolution of prp genes and assess their roles in other enteric pathogens, the structure and distribution of these genes among closely related Shigella subgroups were studied. PCR amplification, probe hybridization studies and DNA sequencing were used to determine the prp genotypes of 58 strains from the four Shigella subgroups, Dysenteriae, Boydii, Sonnei and Flexneri. It was found that the prp alleles among Shigella subgroups were extremely susceptible to gene inactivation and that the mutations involved in prp allele inactivation were varied. They included IS insertions, gene replacement by an IS element, a small deletion within the gene or large deletion engulfing the entire gene region, and base substitutions that generated premature termination codons. As a result, of 58 strains studied, only eight (14 %) possessed intact prpA and prpB genes. Of the Shigella strains examined, 76 % (44/58) showed at least one of the prp alleles inactivated by one or more IS elements, including IS1, IS4, IS600 and IS629. Phylogenetic analysis revealed that IS elements have been independently acquired in multiple lineages of Shigella, suggesting that loss of functional alleles has been advantageous during Shigella strain evolution.
由prpA和prpB基因编码的磷蛋白磷酸酶在大肠杆菌胞外区室中错误折叠蛋白降解的信号转导途径中发挥作用。为了追踪prp基因的进化并评估它们在其他肠道病原体中的作用，研究了这些基因在密切相关的志贺氏菌亚群中的结构和分布。采用聚合酶链反应（PCR）扩增、探针杂交研究和DNA测序来确定来自痢疾志贺氏菌、鲍氏志贺氏菌、宋内志贺氏菌和福氏志贺氏菌这四个志贺氏菌亚群的58株菌株的prp基因型。结果发现，志贺氏菌亚群中的prp等位基因极易发生基因失活，且参与prp等位基因失活的突变多种多样。这些突变包括插入序列（IS）插入、被IS元件取代的基因、基因内的小缺失或包含整个基因区域的大缺失，以及产生过早终止密码子的碱基替换。因此，在所研究的58株菌株中，只有8株（14%）拥有完整的prpA和prpB基因。在检测的志贺氏菌菌株中，76%（44/58）至少有一个prp等位基因被一种或多种IS元件失活，这些IS元件包括IS1、IS4、IS600和IS629。系统发育分析表明，IS元件已在志贺氏菌的多个谱系中独立获得，这表明在志贺氏菌菌株进化过程中，功能性等位基因的丧失是有利的。
