Extensive Cell Envelope Modulation Is Associated with Virulence in Brucella abortus

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• 作者：Julie Lamontagne ; Heather Butler ; Esteban Chaves-Olarte ; Joanna Hunter ; Michael Schirm ; Caroline Paquet ; Mei Tian ; Paul Kearney ; Lyes Hamaidi ; Daniel Chelsky ; Ignacio Moriyó ; n ; Edgardo Moreno ; Eu
• 刊名：Journal of Proteome Research
• 出版年：2007
• 出版时间：April 2007
• 年：2007
• 卷：6
• 期：4
• 页码：1519 - 1529
• 全文大小：947K
• 年卷期：v.6,no.4(April 2007)
• ISSN：1535-3907

文摘

Brucella virulence is linked to components of the cell envelope and tightly connected to the function ofthe BvrR/BvrS sensory-regulatory system. To quantify the impact of BvrR/BvrS on cell envelope proteins,we performed a label-free mass spectrometry-based proteomic analysis of spontaneously releasedouter membrane fragments from four strains of Brucella abortus (wild type virulent, avirulent bvrR^-and bvrS^- mutants as well as reconstituted virulent bvrR⁺ (bvrR^-/pbvrR⁺)). We identified 167 differentiallyexpressed proteins, of which 25 were assigned to the outer membrane. Approximately half of the outermembrane proteins decreased in abundance, whereas half increased. Notably, expression of five Omp3family proteins decreased whereas five lipoproteins increased in the mutant strains. In the periplasmicspace, by contrast, approximately 80% of the 60 differentially expressed proteins were increased in atleast one avirulent mutant. Periplasmic proteins are primarily involved in substrate uptake and transport,and a uniform increase in this class may indicate a nutritional stress response, possibly a consequenceof defective outer membrane function. Virtually all proteins reverted to wild type levels in thereconstituted virulent bvrR⁺ strain. We propose that the wide changes in cell envelope protein expressionrelate to the markedly avirulent phenotype of bvrR^- and bvrS^- mutants and that Brucella virulencedepends on regulatory networks involving cell envelope and metabolism rather than on discretevirulence factors. This model may be relevant to other -Proteobacteria harboring BvrR/BvrS orthologoussystems known to be essential for parasitism or endosymbiosis.