Comparative proteomics analyses reveal the virB of B. melitensis affects expression of intracellular survival related proteins.
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.
Wang
Yufei
Y
Institute of Disease Control and Prevention, Academy of Military Medical Science, Beijing, China.
Chen
Zeliang
Z
Qiao
Feng
F
Ying
Tianyi
T
Yuan
Jing
J
Zhong
Zhijun
Z
Zhou
Lei
L
Du
Xinying
X
Wang
Zhoujia
Z
Zhao
Jin
J
Dong
Shicun
S
Jia
Leili
L
Yuan
Xitong
X
Yang
Ruifu
R
Sun
Yansong
Y
Huang
Liuyu
L
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
D001426:Bacterial Proteins; D017931:DNA Primers; D004269:DNA, Bacterial