<?xml version="1.0" encoding="UTF-8"?><xml><records><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Siegrist, M Sloan</style></author><author><style face="normal" font="default" size="100%">Steigedal, Magnus</style></author><author><style face="normal" font="default" size="100%">Ahmad, Rushdy</style></author><author><style face="normal" font="default" size="100%">Mehra, Alka</style></author><author><style face="normal" font="default" size="100%">Dragset, Marte S</style></author><author><style face="normal" font="default" size="100%">Schuster, Brian M</style></author><author><style face="normal" font="default" size="100%">Philips, Jennifer A</style></author><author><style face="normal" font="default" size="100%">Carr, Steven A</style></author><author><style face="normal" font="default" size="100%">Rubin, Eric J</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Mycobacterial Esx-3 requires multiple components for iron acquisition.</style></title><secondary-title><style face="normal" font="default" size="100%">MBio</style></secondary-title><alt-title><style face="normal" font="default" size="100%">MBio</style></alt-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Bacterial Secretion Systems</style></keyword><keyword><style  face="normal" font="default" size="100%">Gene Order</style></keyword><keyword><style  face="normal" font="default" size="100%">Genetic Loci</style></keyword><keyword><style  face="normal" font="default" size="100%">Iron</style></keyword><keyword><style  face="normal" font="default" size="100%">Mycobacterium</style></keyword><keyword><style  face="normal" font="default" size="100%">Oxazoles</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2014</style></year><pub-dates><date><style  face="normal" font="default" size="100%">2014</style></date></pub-dates></dates><volume><style face="normal" font="default" size="100%">5</style></volume><pages><style face="normal" font="default" size="100%">e01073-14</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">&lt;p&gt;ABSTRACT The type VII secretion systems are conserved across mycobacterial species and in many Gram-positive bacteria. While the well-characterized Esx-1 pathway is required for the virulence of pathogenic mycobacteria and conjugation in the model organism Mycobacterium smegmatis, Esx-3 contributes to mycobactin-mediated iron acquisition in these bacteria. Here we show that several Esx-3 components are individually required for function under low-iron conditions but that at least one, the membrane-bound protease MycP3 of M. smegmatis, is partially expendable. All of the esx-3 mutants tested, including the ΔmycP3ms mutant, failed to export the native Esx-3 substrates EsxHms and EsxGms to quantifiable levels, as determined by targeted mass spectrometry. Although we were able to restore low-iron growth to the esx-3 mutants by genetic complementation, we found a wide range of complementation levels for protein export. Indeed, minute quantities of extracellular EsxHms and EsxGms were sufficient for iron acquisition under our experimental conditions. The apparent separation of Esx-3 function in iron acquisition from robust EsxGms and EsxHms secretion in the ΔmycP3ms mutant and in some of the complemented esx-3 mutants compels reexamination of the structure-function relationships for type VII secretion systems. IMPORTANCE Mycobacteria have several paralogous type VII secretion systems, Esx-1 through Esx-5. Whereas Esx-1 is required for pathogenic mycobacteria to grow within an infected host, Esx-3 is essential for growth in vitro. We and others have shown that Esx-3 is required for siderophore-mediated iron acquisition. In this work, we identify individual Esx-3 components that contribute to this process. As in the Esx-1 system, most mutations that abolish Esx-3 protein export also disrupt its function. Unexpectedly, however, ultrasensitive quantitation of Esx-3 secretion by multiple-reaction-monitoring mass spectrometry (MRM-MS) revealed that very low levels of export were sufficient for iron acquisition under similar conditions. Although protein export clearly contributes to type VII function, the relationship is not absolute.&lt;/p&gt;</style></abstract><issue><style face="normal" font="default" size="100%">3</style></issue><custom1><style face="normal" font="default" size="100%">http://www.ncbi.nlm.nih.gov/pubmed/24803520?dopt=Abstract</style></custom1></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Siegrist, M Sloan</style></author><author><style face="normal" font="default" size="100%">Unnikrishnan, Meera</style></author><author><style face="normal" font="default" size="100%">McConnell, Matthew J</style></author><author><style face="normal" font="default" size="100%">Borowsky, Mark</style></author><author><style face="normal" font="default" size="100%">Cheng, Tan-Yun</style></author><author><style face="normal" font="default" size="100%">Siddiqi, Noman</style></author><author><style face="normal" font="default" size="100%">Fortune, Sarah M</style></author><author><style face="normal" font="default" size="100%">Moody, D Branch</style></author><author><style face="normal" font="default" size="100%">Rubin, Eric J</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Mycobacterial Esx-3 is required for mycobactin-mediated iron acquisition.</style></title><secondary-title><style face="normal" font="default" size="100%">Proc Natl Acad Sci U S A</style></secondary-title><alt-title><style face="normal" font="default" size="100%">Proc. Natl. Acad. Sci. U.S.A.</style></alt-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Animals</style></keyword><keyword><style  face="normal" font="default" size="100%">Bacterial Proteins</style></keyword><keyword><style  face="normal" font="default" size="100%">Genome, Bacterial</style></keyword><keyword><style  face="normal" font="default" size="100%">Iron</style></keyword><keyword><style  face="normal" font="default" size="100%">Macrophages</style></keyword><keyword><style  face="normal" font="default" size="100%">Mice</style></keyword><keyword><style  face="normal" font="default" size="100%">Mutation</style></keyword><keyword><style  face="normal" font="default" size="100%">Mycobacterium</style></keyword><keyword><style  face="normal" font="default" size="100%">Mycobacterium Infections</style></keyword><keyword><style  face="normal" font="default" size="100%">Oxazoles</style></keyword><keyword><style  face="normal" font="default" size="100%">Protein Binding</style></keyword><keyword><style  face="normal" font="default" size="100%">Secretory Pathway</style></keyword><keyword><style  face="normal" font="default" size="100%">Siderophores</style></keyword><keyword><style  face="normal" font="default" size="100%">Transcription, Genetic</style></keyword><keyword><style  face="normal" font="default" size="100%">Up-Regulation</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2009</style></year><pub-dates><date><style  face="normal" font="default" size="100%">2009 Nov 3</style></date></pub-dates></dates><volume><style face="normal" font="default" size="100%">106</style></volume><pages><style face="normal" font="default" size="100%">18792-7</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">&lt;p&gt;The Esx secretion pathway is conserved across Gram-positive bacteria. Esx-1, the best-characterized system, is required for virulence of Mycobacterium tuberculosis, although its precise function during infection remains unclear. Esx-3, a paralogous system present in all mycobacterial species, is required for growth in vitro. Here, we demonstrate that mycobacteria lacking Esx-3 are defective in acquiring iron. To compete for the limited iron available in the host and the environment, these organisms use mycobactin, high-affinity iron-binding molecules. In the absence of Esx-3, mycobacteria synthesize mycobactin but are unable to use the bound iron and are impaired severely for growth during macrophage infection. Mycobacteria thus require a specialized secretion system for acquiring iron from siderophores.&lt;/p&gt;</style></abstract><issue><style face="normal" font="default" size="100%">44</style></issue><custom1><style face="normal" font="default" size="100%">http://www.ncbi.nlm.nih.gov/pubmed/19846780?dopt=Abstract</style></custom1></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Siegrist, M Sloan</style></author><author><style face="normal" font="default" size="100%">Rubin, Eric J</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Phage transposon mutagenesis.</style></title><secondary-title><style face="normal" font="default" size="100%">Methods Mol Biol</style></secondary-title><alt-title><style face="normal" font="default" size="100%">Methods Mol. Biol.</style></alt-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Bacteriophages</style></keyword><keyword><style  face="normal" font="default" size="100%">DNA Transposable Elements</style></keyword><keyword><style  face="normal" font="default" size="100%">Mutagenesis</style></keyword><keyword><style  face="normal" font="default" size="100%">Mutation</style></keyword><keyword><style  face="normal" font="default" size="100%">Mycobacterium</style></keyword><keyword><style  face="normal" font="default" size="100%">Transduction, Genetic</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2009</style></year><pub-dates><date><style  face="normal" font="default" size="100%">2009</style></date></pub-dates></dates><volume><style face="normal" font="default" size="100%">465</style></volume><pages><style face="normal" font="default" size="100%">311-23</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">&lt;p&gt;Phage transduction is an attractive method of genetic manipulation in mycobacteria. PhiMycoMarT7 is well suited for transposon mutagenesis as it is temperature sensitive for replication and contains T7 promoters that promote transcription, a highly active transposase gene, and an Escherichia coli oriR6 K origin of replication. Mycobacterial transposon mutant libraries produced by PhiMycoMarT7 transduction are amenable to both forward and reverse genetic studies. In this protocol, we detail the preparation of PhiMycoMarT7, including a description of the phage, reconstitution of the phage, purification of plaques, preparation of phage stock, and titering of phage stock. We then describe the transduction procedure and finally outline the isolation of individual transposon mutants.&lt;/p&gt;</style></abstract><custom1><style face="normal" font="default" size="100%">http://www.ncbi.nlm.nih.gov/pubmed/20560067?dopt=Abstract</style></custom1></record></records></xml>