title: Comparative proteomics analyses reveal the virB of B. melitensis affects expression of intracellular survival related proteins.
abstract: BACKGROUND
  Brucella melitensis is a facultative, intracellular, pathogenic bacterium that replicates within macrophages. The type IV secretion system encoded by the virB operon (virB) is involved in Brucella intracellular survival. However, the underlying molecular mechanisms, especially the target proteins affected by the virB, remain largely unclear.
  
  
  RESULTS
  In order to define the proteins affected by virB, the proteomes of wild-type and the virB mutant were compared under in vitro conditions where virB was highly activated. The differentially expressed proteins were identified by MALDI-TOF-MS. Forty-four down-regulated and eighteen up-regulated proteins which exhibited a 2-fold or greater change were identified. These proteins included those involved in amino acid transport and metabolism, lipid metabolism, energy production, cell membrane biogenesis, translation, post-translational modifications and protein turnover, as well as unknown proteins. Interestingly, several important virulence related proteins involved in intracellular survival, including VjbR, DnaK, HtrA, Omp25, and GntR, were down-regulated in the virB mutant. Transcription analysis of virB and vjbR at different growth phase showed that virB positively affect transcription of vjbR in a growth phase dependent manner. Quantitative RT-PCR showed that transcription of these genes was also affected by virB during macrophage cell infection, consistent with the observed decreased survival of the virB mutant in macrophage.
  
  
  CONCLUSIONS
  These data indicated that the virB operon may control the intracellular survival of Brucella by affecting the expression of relevant proteins.
authors.affiliation: Institute of Disease Control and Prevention, Academy of Military Medical Science, Beijing, China.
authors.forename: Yufei
authors.initials: Y
authors.lastname: Wang
authors.forename: Zeliang
authors.initials: Z
authors.lastname: Chen
authors.forename: Feng
authors.initials: F
authors.lastname: Qiao
authors.forename: Tianyi
authors.initials: T
authors.lastname: Ying
authors.forename: Jing
authors.initials: J
authors.lastname: Yuan
authors.forename: Zhijun
authors.initials: Z
authors.lastname: Zhong
authors.forename: Lei
authors.initials: L
authors.lastname: Zhou
authors.forename: Xinying
authors.initials: X
authors.lastname: Du
authors.forename: Zhoujia
authors.initials: Z
authors.lastname: Wang
authors.forename: Jin
authors.initials: J
authors.lastname: Zhao
authors.forename: Shicun
authors.initials: S
authors.lastname: Dong
authors.forename: Leili
authors.initials: L
authors.lastname: Jia
authors.forename: Xitong
authors.initials: X
authors.lastname: Yuan
authors.forename: Ruifu
authors.initials: R
authors.lastname: Yang
authors.forename: Yansong
authors.initials: Y
authors.lastname: Sun
authors.forename: Liuyu
authors.initials: L
authors.lastname: Huang
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D001483:Base Sequence; D017347:Brucella melitensis / Q000235:genetics* / Q000378:metabolism* / Q000472:pathogenicity; D002460:Cell Line; D017931:DNA Primers / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics; D015870:Gene Expression; D005798:Genes, Bacterial; D054884:Host-Pathogen Interactions; D008264:Macrophages / Q000378:metabolism / Q000382:microbiology; D051379:Mice; D009154:Mutation; D009876:Operon; D040901:Proteomics; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014774:Virulence
chemical_list: D001426:Bacterial Proteins; D017931:DNA Primers; D004269:DNA, Bacterial