Open AccessThe Cyclic Nucleotide Monophosphate Domain of Xanthomonas campestris Global Regulator Clp Defines a New Class of Cyclic Di-GMP Effectors
Author(s) -
Fei Tao,
Yanan He,
Donghui Wu,
Sanjay Swarup,
Lian-Hui Zhang
Publication year - 2010
Publication title -
journal of bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.652
H-Index - 246
eISSN - 1067-8832
pISSN - 0021-9193
DOI - 10.1128/jb.01253-09
Subject(s) - xanthomonas campestris , biology , regulon , effector , allosteric regulation , virulence , response regulator , second messenger system , biochemistry , serine , signal transduction , gene , regulation of gene expression , mutant , receptor , phosphorylation
The widely conserved second messenger cyclic diguanosine monophosphate (c-di-GMP) plays a key role in quorum-sensing (QS)-dependent production of virulence factors inXanthomonas campestris pv. campestris. The detection of QS diffusible signal factor (DSF) by the sensor RpfC leads to the activation of response regulator RpfG, which activates virulence gene expression by degrading c-di-GMP. Here, we show that a global regulator in theX. campestris pv. campestris QS regulatory pathway, Clp, is a c-di-GMP effector. c-di-GMP specifically binds to Clp with high affinity and induces allosteric conformational changes that abolish the interaction between Clp and its target gene promoter. Clp is similar to the cyclic AMP (cAMP) binding proteins Crp and Vfr and contains a conserved cyclic nucleotide monophosphate (cNMP) binding domain. Using site-directed mutagenesis, we found that the cNMP binding domain of Clp contains a glutamic acid residue (E99) that is essential for c-di-GMP binding. Substituting the residue with serine (E99S) resulted in decreased sensitivity to changes in the intracellular c-di-GMP level and attenuated bacterial virulence. These data establish the direct role of Clp in the response to fluctuating c-di-GMP levels and depict a novel mechanism by which QS links the second messenger with theX. campestris pv. campestris virulence regulon.