Litwin C M, Quackenbush J
Section of Clinical Immunology, Microbiology and Virology, Salt Lake City, Utah, 84132, USA.
Microb Pathog. 2001 Dec;31(6):295-307. doi: 10.1006/mpat.2001.0472.
In Vibrio vulnificus, the ability to acquire iron from the host has been shown to correlate with virulence. Here, we show that the DNA upstream of hupA (haem uptake receptor) in V. vulnificus encodes a protein in the inverse orientation to hupA (named hupR). HupR shares homology with the LysR family of positive transcriptional activators. A hupA-lacZ fusion contained on a plasmid was transformed into Fur(-), Fur(+)and HupR(-)strains of V. vulnificus. The beta-galactosidase assays and Northern blot analysis showed that transcription of hupA is negatively regulated by iron and the Fur repressor in V. vulnificus. Under low-iron conditions with added haemin, the expression of hupA in the hupR mutant was significantly lower than in the wild-type. This diminished response to haem was detected by both Northern blot and hupA-lacZ fusion analysis. The haem response of hupA in the hupR mutant was restored to wild-type levels when complemented with hupR in trans. These studies suggest that HupR may act as a positive regulator of hupA transcription under low-iron conditions in the presence of haemin.
在创伤弧菌中,从宿主获取铁的能力已被证明与毒力相关。在此,我们表明创伤弧菌中hupA(血红素摄取受体)上游的DNA以与hupA相反的方向编码一种蛋白质(命名为hupR)。HupR与阳性转录激活因子的LysR家族具有同源性。将质粒上携带的hupA - lacZ融合体转化到创伤弧菌的Fur(-)、Fur(+)和HupR(-)菌株中。β - 半乳糖苷酶测定和Northern印迹分析表明,创伤弧菌中hupA的转录受铁和Fur阻遏物的负调控。在添加血红素的低铁条件下,hupR突变体中hupA的表达明显低于野生型。通过Northern印迹和hupA - lacZ融合分析均检测到对血红素的这种反应减弱。当用hupR进行反式互补时,hupR突变体中hupA的血红素反应恢复到野生型水平。这些研究表明,在低铁条件下且存在血红素时,HupR可能作为hupA转录的正调控因子发挥作用。