IRON ACQUISITION BY MYCOBACTERIUM-TUBERCULOSIS - ISOLATION AND CHARACTERIZATION OF A FAMILY OF IRON-BINDING EXOCHELINS
IRON ACQUISITION BY MYCOBACTERIUM-TUBERCULOSIS - ISOLATION AND CHARACTERIZATION OF A FAMILY OF IRON-BINDING EXOCHELINS
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DOI：
10.1073/pnas.92.11.5189
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发表时间：
1995-05-23
影响因子：
11.1
通讯作者：
HORWITZ, MA
中科院分区：
文献类型：
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作者：
GOBIN, J;MOORE, CH;HORWITZ, MA
结核分枝杆菌是结核病的主要病原体，必须从宿主获得铁才能引起感染。为了做到这一点，它释放出高亲和力的铁结合铁载体，称为外螯素。外螯素被认为是将铁转移到细菌细胞壁中的另一种高亲和力铁结合分子-分枝杆菌素上，以供细菌随后利用。结核病及其质谱表征，外螯素包括一类分子，其最丰富的种类在中性Fe 3+负载状态下的质量范围为744至800 Ha。这些分子形成两个14-Da增量系列，一个饱和的和另一个不饱和的，增量反映侧链上不同数目的CH 2基团。这些系列进一步细分为含丝氨酸或苏氨酸的种类。毒力M.结核Erdman株和无毒M.结核H37 Ra菌株产生类似的一组外螯素。基于它们的串联质谱的比较，外螯素与分枝杆菌素共享共同的核心结构。然而，由于较短的烷基侧链，外螯素比分枝杆菌素小，并且外螯素的侧链终止于甲酯。这些差异使得外螯素比亲脂性分枝杆菌素极性更大，因此可溶于细菌的水性细胞外环境中，其中它们结合宿主中的铁。
Mycobacterium tuberculosis, the primary agent of tuberculosis, must acquire iron from the host to cause infection. To do so, it releases high-affinity iron-binding siderophores called exochelins. Exochelins are thought to transfer iron to another type of high-affinity iron-binding molecule in the bacterial cell wall, mycobactins, for subsequent utilization by the bacterium, In this paper, we describe the purification of exochelins of M. tuberculosis and their characterization by mass spectrometry, Exochelins comprise a family of molecules whose most abundant species range in mass from 744 to 800 Ha in the neutral Fe3+-loaded state. The molecules form two 14-Da-increment series, one saturated and the other unsaturated, with the increments reflecting different numbers of CH2 groups on a side chain, These series further subdivide into serine- or threonine-containing species. The virulent M. tuberculosis Erdman strain and the avirulent M. tuberculosis H37Ra strain produce a similar set of exochelins. Based on a comparison of their tandem mass spectra, exochelins share a common core structure with mycobactins. However, exochelins are smaller than mycobactins due to a shorter alkyl side chain, and the side chain of exochelins terminates in a methyl ester, These differences render exochelins more polar than the lipophilic mycobactins and hence soluble in the aqueous extracellular milieu of the bacterium in which they bind iron in the host.