PDF(Pubmed)
Abstract：
bb0616 of Borrelia burgdorferi, the Lyme disease pathogen, encodes a hypothetical protein of unknown function. In this study, we showed that BB0616 was not surface-exposed or associated with the membrane through localization analyses using proteinase K digestion and cell partitioning assays. The expression of bb0616 was influenced by a reduced pH but not by growth phases, elevated temperatures, or carbon sources during in vitro cultivation. A transcriptional start site for bb0616 was identified by using 5\' rapid amplification of cDNA ends, which led to the identification of a functional promoter in the 5\' regulatory region upstream of bb0616. By analyzing a bb0616-deficient mutant and its isogenic complemented counterparts, we found that the infectivity potential of the mutant was significantly attenuated. The inactivation of bb0616 displayed no effect on borrelial growth in the medium or resistance to oxidative stress, but the mutant was significantly more susceptible to osmotic stress. In addition, the production of global virulence regulators such as BosR and RpoS as well as virulence-associated outer surface lipoproteins OspC and DbpA was reduced in the mutant. These phenotypes were fully restored when gene mutation was complemented with a wild-type copy of bb0616. Based on these findings, we concluded that the hypothetical protein BB0616 is required for the optimal infectivity of B. burgdorferi, potentially by impacting B. burgdorferi virulence gene expression as well as survival of the spirochete under stressful conditions.
摘要：
伯氏疏螺旋体b0616,莱姆病病原体,编码一种功能未知的假设蛋白质。在这项研究中,通过使用蛋白酶K消化和细胞分配测定的定位分析,我们显示BB0616没有表面暴露或与膜相关.bb0616的表达受pH降低的影响，但不受生长期的影响，升高的温度,或在体外培养过程中的碳源。bb0616的转录起始位点通过使用cDNA末端的5'快速扩增来鉴定，这导致在bb0616上游的5'调控区中鉴定出一个功能性启动子。通过分析bb0616缺陷突变体及其同基因互补的对应物，我们发现该突变体的感染性潜能显著减弱.bb0616的失活对培养基中的疏螺旋体生长或对氧化应激的抗性没有影响，但突变体明显更容易受到渗透胁迫。此外,在突变体中,总体毒力调节因子如BosR和RpoS以及与毒力相关的外表面脂蛋白OspC和DbpA的产生减少。当用bb0616的野生型拷贝补充基因突变时,这些表型完全恢复。基于这些发现,我们得出的结论是，假设的蛋白质BB0616是B.burgdorferi的最佳感染性所必需的，可能会影响B.burgdorferi毒力基因的表达以及螺旋体在压力条件下的存活。
