The response of the TonB-dependent transport network in Anabaena sp. PCC 7120 to cell density and metal availability
The response of the TonB-dependent transport network in Anabaena sp. PCC 7120 to cell density and metal availability
复制标题
鱼腥藻依赖于 TonB 的运输网络的响应。
DOI：
10.1007/s10534-013-9644-0
复制
发表时间：
2013
期刊：
影响因子：
3.5
通讯作者：
E. Schleiff
中科院分区：
文献类型：
--
作者：
M. Stevanovic;C. Lehmann;E. Schleiff
TonB依赖性转运蛋白（TBDT）是细菌中参与摄取多种分子（如铁载体螯合铁）的必需蛋白家族，铁载体螯合铁是第一个被描述的底物。同时，已知TBDTs参与许多金属、糖和多肽的摄取。TBDTs的作用由质膜锚定的TonB调节和供能，TonB由质子泵充电。不同物种中编码TBDTs的基因数目不同，这可能反映了系统的环境适应或进化变异。例如，在蓝细菌鱼腥藻PCC 7120中，已经鉴定了大量的22个编码TBDT的基因，并且已经探索了这些基因在不存在铁或铜以及在氮饥饿下的表达。我们描述了TBDT基因的表达和相应的细胞质膜定位组件的分析，后者似乎有一个较低程度的复杂性鱼腥藻属PCC 7120。该分析揭示了反应不仅取决于金属供应，而且还取决于细胞培养密度。此外，我们提出了一个大组的FhuA样基因，在标准条件下表达最高，这表明铁或铜运输不同的功能。根据表达谱和我们的理解的运输系统的鱼腥藻PCC 7120的后果进行了讨论的基因聚类。
TonB dependent transporters (TBDT) are an essential protein family in bacteria involved in the uptake of a broad variety of molecules such as siderophore-chelated iron, which was the first described substrate. Meanwhile it is known that TBDTs are involved in the uptake of many metals, sugars and polypeptides. The action of TBDTs is regulated and energized by the plasma membrane anchored TonB, which is charged by a proton pump. The number of the genes coding for TBDTs varies in different species, which might reflect environmental adaptations or evolutionary variations of the system. For example, in the cyanobacterium Anabaena sp. PCC 7120 the large number of 22 genes coding for TBDTs has been identified and the expression of these genes has been explored in the absence of iron or copper as well as under nitrogen starvation. We describe the analysis of the expression of the TBDT genes and the according cytoplasmic-membrane localized components; the latter appear to have a lower degree of complexity in Anabaena sp. PCC 7120. This analysis unravels that the response is not sole dependent on the metal supply, but also on cell culture densities. In addition, we present a large group of FhuA-like genes which is expressed highest under standard conditions suggesting a function distinct from iron or copper transport. The genes are clustered according to the expression profile and the consequences for our understanding of the transport systems in Anabaena sp. PCC 7120 are discussed.