The Zur of Xanthomonas campestris functions as a repressor and an activator of putative zinc homeostasis genes via recognizing two distinct sequences within its target promoters.
It has been long considered that zinc homeostasis in bacteria is maintained by export systems and uptake systems, which are separately controlled by their own regulators and the uptake systems are negatively regulated by Zur which binds to an about 30-bp AT-rich sequence known as Zur-box present in its target promoters to block the entry of RNA polymerase. Here, we demonstrated in vivo and in vitro that in addition to act as a repressor of putative Zn(2+)-uptake systems, the Zur of the bacterial phytopathogen Xanthomonas campestris pathovar campestris (Xcc) acts as an activator of a Zn(2+) efflux pump. The Xcc Zur binds to a similar Zur-box with approximately 30-bp AT-rich sequence in the promoters of the genes encoding putative Zn(2+)-uptake systems but a 59-bp GC-rich sequence with a 20-bp inverted repeat overlapping the promoter's -35 to -10 sequence of the gene encoding a Zn(2+)-export system. Mutagenesis of the inverted repeat sequence resulted in abolishment of the in vitro binding and the in vivo and in vitro activation of the export gene's promoter by Zur. These results reveal that the Xcc Zur functions as a repressor and an activator of putative zinc homeostasis genes via recognizing two distinct sequences within its target promoters.
Huang
Dong-Liang
DL
The Key Laboratory of Ministry of Education for Microbial and Plant Genetic Engineering, and College of Life Science and Technology, Guangxi University, 100 Daxue Road, Nanning Guangxi 530004, China.
Tang
Dong-Jie
DJ
Liao
Qing
Q
Li
Heng-Cong
HC
Chen
Qi
Q
He
Yong-Qiang
YQ
Feng
Jia-Xun
JX
Jiang
Bo-Le
BL
Lu
Guang-Tao
GT
Chen
Baoshan
B
Tang
Ji-Liang
JL
D001426:Bacterial Proteins / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites; D027682:Cation Transport Proteins / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D006706:Homeostasis; D008670:Metals / Q000378:metabolism; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D012091:Repetitive Sequences, Nucleic Acid; D012097:Repressor Proteins / Q000378:metabolism; D015534:Trans-Activators / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D016959:Xanthomonas campestris / Q000235:genetics*; D015032:Zinc / Q000378:metabolism*
D001426:Bacterial Proteins; D027682:Cation Transport Proteins; D008670:Metals; D012097:Repressor Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D015032:Zinc