OBJECTIVETo investigate the functional relations between the putative proteins YpCD1.08, YpCD1.09, YpCD1.16 encoded in pCD1 plasmid of Yersinia pestis and its type III secretion system (T3SS).

METHODSMutants of YpCD1.08, YpCD1.09, YpCD1.16 were constructed using λ-Red recombinant system. The growth curves of the mutant strains cultivated in TMH medium with or without calcium at 26 °C and 37 °C were determined to analyze the low calcium response phenotype. The transcription levels of ΔYpCD1.08, ΔYpCD1.09, ΔYpCD1.16 in Yersinia pestis and the dependence to temperature were determined using real time RT-PCR after cultivation at 26 °C and 37 °C and extraction of RNA. A β-lactamases reporter system was adopted to study the influence of these genes on the translocation of effector YopE of T3SS.

RESULTSWhen grown in TMH medium without calcium at 26 °C and 37 °C, the growth curve of the YpCD1.08, YpCD1.09, YpCD1.16 mutants were similar to that of the wild-type strain, indicating that the low calcium response of all the mutants were normal. The ratios of YpCD1.08, YpCD1.09, YpCD1.16 gene transcriptional level at 37 °C and 26 °C were 2.3 ± 0.3, 2.3 ± 0.5 and 3.2 ± 0.7, respectively, indicating that these genes were transcribed in Yersinia pestis and their transcription regulations showed a temperature-dependence that was consistent with the well established temperature-dependent expression of Yersinia T3SS genes. The β-lactamases reporter assays demonstrated that ΔYpCD1.08 could translocate much higher level of YopE into HeLa cells, since that the light intensity ratio of 477/520 nm at 140 min was 2.5, whereas it was 1.8 for the wild-type strain, and the values in ΔYpCD1.09 and ΔYpCD1.16 were similar to the wild-type strain.

CONCLUSIONYpCD1.08, YpCD1.09, YpCD1.16 gene are likely to be the new members of T3SS, and the putative protein YpCD1.08 could play some roles in YopE secretion and translocation.

Bacterial Outer Membrane Proteins ; secretion ; Bacterial Secretion Systems ; genetics ; Genes, Bacterial ; Plasmids ; Protein Interaction Mapping ; Yersinia pestis ; genetics ; metabolism ; pathogenicity

Brucella is a facultative intracellular pathogen that causes infection in domestic animal and humans,mainly parasitizing in cells and macrophages of hosts.Brucella can lead to abortion and sterility in animals.Meanwhile,it also causes arthralgia,weakness,undulat fever,hepatosplenomegaly and other symptoms in humans.Brucella relies on immune escape mechanism in the confrontation with the host.It can help Brucella "camouflage" to evade the identification of the immune system of the hosts and replicate within cells to persist to establish a long-term infection in the host.As a result of the existence of this mechanism,the treatment of Brucella infection is quite difficult.Type Ⅳ secretion system (T4SS) is a key virulence factor and it is essential for Brucella to survive in host cells.The effector proteins secreted by T4SS can help regulate the immune response against Brucella.In this article,we reviewed the studies on related proteins of the type Ⅳ secretion system of Brucella and its immune response,especially the relationship between the secretions of effector proteins mediated by VirB operon and immunity of the host.