Discovery of a siderophore export system essential for virulence of Mycobacterium tuberculosis.

Iron is an essential nutrient for most bacterial pathogens, but is restricted by the host immune system. Mycobacterium tuberculosis (Mtb) utilizes two classes of small molecules, mycobactins and carboxymycobactins, to capture iron from the human host. Here, we show that an Mtb mutant lacking the mmp...

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Autores principales:	Ryan M Wells, Christopher M Jones, Zhaoyong Xi, Alexander Speer, Olga Danilchanka, Kathryn S Doornbos, Peibei Sun, Fangming Wu, Changlin Tian, Michael Niederweis
Formato:	article
Lenguaje:	EN
Publicado:	Public Library of Science (PLoS) 2013
Materias:	Immunologic diseases. Allergy RC581-607 Biology (General) QH301-705.5
Acceso en línea:	https://doaj.org/article/594c56aa3fef4488ad8a61059f35372d
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spelling	oai:doaj.org-article:594c56aa3fef4488ad8a61059f35372d2021-11-18T06:06:05ZDiscovery of a siderophore export system essential for virulence of Mycobacterium tuberculosis.1553-73661553-737410.1371/journal.ppat.1003120https://doaj.org/article/594c56aa3fef4488ad8a61059f35372d2013-01-01T00:00:00Zhttps://www.ncbi.nlm.nih.gov/pmc/articles/pmid/23431276/?tool=EBIhttps://doaj.org/toc/1553-7366https://doaj.org/toc/1553-7374Iron is an essential nutrient for most bacterial pathogens, but is restricted by the host immune system. Mycobacterium tuberculosis (Mtb) utilizes two classes of small molecules, mycobactins and carboxymycobactins, to capture iron from the human host. Here, we show that an Mtb mutant lacking the mmpS4 and mmpS5 genes did not grow under low iron conditions. A cytoplasmic iron reporter indicated that the double mutant experienced iron starvation even under high-iron conditions. Loss of mmpS4 and mmpS5 did not change uptake of carboxymycobactin by Mtb. Thin layer chromatography showed that the ΔmmpS4/S5 mutant was strongly impaired in biosynthesis and secretion of siderophores. Pull-down experiments with purified proteins demonstrated that MmpS4 binds to a periplasmic loop of the associated transporter protein MmpL4. This interaction was corroborated by genetic experiments. While MmpS5 interacted only with MmpL5, MmpS4 interacted with both MmpL4 and MmpL5. These results identified MmpS4/MmpL4 and MmpS5/MmpL5 as siderophore export systems in Mtb and revealed that the MmpL proteins transport small molecules other than lipids. MmpS4 and MmpS5 resemble periplasmic adapter proteins of tripartite efflux pumps of Gram-negative bacteria, however, they are not only required for export but also for efficient siderophore synthesis. Membrane association of MbtG suggests a link between siderophore synthesis and transport. The structure of the soluble domain of MmpS4 (residues 52-140) was solved by NMR and indicates that mycobacterial MmpS proteins constitute a novel class of transport accessory proteins. The bacterial burden of the mmpS4/S5 deletion mutant in mouse lungs was lower by 10,000-fold and none of the infected mice died within 180 days compared to wild-type Mtb. This is the strongest attenuation observed so far for Mtb mutants lacking genes involved in iron utilization. In conclusion, this study identified the first components of novel siderophore export systems which are essential for virulence of Mtb.Ryan M WellsChristopher M JonesZhaoyong XiAlexander SpeerOlga DanilchankaKathryn S DoornbosPeibei SunFangming WuChanglin TianMichael NiederweisPublic Library of Science (PLoS)articleImmunologic diseases. AllergyRC581-607Biology (General)QH301-705.5ENPLoS Pathogens, Vol 9, Iss 1, p e1003120 (2013)
institution	DOAJ
collection	DOAJ
language	EN
topic	Immunologic diseases. Allergy RC581-607 Biology (General) QH301-705.5
spellingShingle	Immunologic diseases. Allergy RC581-607 Biology (General) QH301-705.5 Ryan M Wells Christopher M Jones Zhaoyong Xi Alexander Speer Olga Danilchanka Kathryn S Doornbos Peibei Sun Fangming Wu Changlin Tian Michael Niederweis Discovery of a siderophore export system essential for virulence of Mycobacterium tuberculosis.
description	Iron is an essential nutrient for most bacterial pathogens, but is restricted by the host immune system. Mycobacterium tuberculosis (Mtb) utilizes two classes of small molecules, mycobactins and carboxymycobactins, to capture iron from the human host. Here, we show that an Mtb mutant lacking the mmpS4 and mmpS5 genes did not grow under low iron conditions. A cytoplasmic iron reporter indicated that the double mutant experienced iron starvation even under high-iron conditions. Loss of mmpS4 and mmpS5 did not change uptake of carboxymycobactin by Mtb. Thin layer chromatography showed that the ΔmmpS4/S5 mutant was strongly impaired in biosynthesis and secretion of siderophores. Pull-down experiments with purified proteins demonstrated that MmpS4 binds to a periplasmic loop of the associated transporter protein MmpL4. This interaction was corroborated by genetic experiments. While MmpS5 interacted only with MmpL5, MmpS4 interacted with both MmpL4 and MmpL5. These results identified MmpS4/MmpL4 and MmpS5/MmpL5 as siderophore export systems in Mtb and revealed that the MmpL proteins transport small molecules other than lipids. MmpS4 and MmpS5 resemble periplasmic adapter proteins of tripartite efflux pumps of Gram-negative bacteria, however, they are not only required for export but also for efficient siderophore synthesis. Membrane association of MbtG suggests a link between siderophore synthesis and transport. The structure of the soluble domain of MmpS4 (residues 52-140) was solved by NMR and indicates that mycobacterial MmpS proteins constitute a novel class of transport accessory proteins. The bacterial burden of the mmpS4/S5 deletion mutant in mouse lungs was lower by 10,000-fold and none of the infected mice died within 180 days compared to wild-type Mtb. This is the strongest attenuation observed so far for Mtb mutants lacking genes involved in iron utilization. In conclusion, this study identified the first components of novel siderophore export systems which are essential for virulence of Mtb.
format	article
author	Ryan M Wells Christopher M Jones Zhaoyong Xi Alexander Speer Olga Danilchanka Kathryn S Doornbos Peibei Sun Fangming Wu Changlin Tian Michael Niederweis
author_facet	Ryan M Wells Christopher M Jones Zhaoyong Xi Alexander Speer Olga Danilchanka Kathryn S Doornbos Peibei Sun Fangming Wu Changlin Tian Michael Niederweis
author_sort	Ryan M Wells
title	Discovery of a siderophore export system essential for virulence of Mycobacterium tuberculosis.
title_short	Discovery of a siderophore export system essential for virulence of Mycobacterium tuberculosis.
title_full	Discovery of a siderophore export system essential for virulence of Mycobacterium tuberculosis.
title_fullStr	Discovery of a siderophore export system essential for virulence of Mycobacterium tuberculosis.
title_full_unstemmed	Discovery of a siderophore export system essential for virulence of Mycobacterium tuberculosis.
title_sort	discovery of a siderophore export system essential for virulence of mycobacterium tuberculosis.
publisher	Public Library of Science (PLoS)
publishDate	2013
url	https://doaj.org/article/594c56aa3fef4488ad8a61059f35372d
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Discovery of a siderophore export system essential for virulence of Mycobacterium tuberculosis.

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