Zinc is an inhibitor of the LdtR transcriptional activator

• Published in: PloS one Vol. 13; no. 4; p. e0195746
• Main Authors: Pagliai, Fernando A, Pan, Lei, Silva, Danilo, Gonzalez, Claudio F, Lorca, Graciela L
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 10-04-2018; Public Library of Science (PLoS)
• Subjects: Affinity; Antibiotics; Bacterial diseases; Biology and Life Sciences; Calorimetry; Cell walls; Citrus fruits; Citrus greening; Citrus paradisi; Deoxyribonucleic acid; DNA; Drug resistance; E coli; Electrophoretic mobility; Escherichia coli; Food; Gene expression; Genes; Genetic aspects; Genetics; Ligands; Mutagenesis; Physical Sciences; Physiological aspects; Physiology; Plant diseases; Plasmids; Proteins; Pseudomonas aeruginosa; Regulators; Research and Analysis Methods; Rhizobium; Site-directed mutagenesis; Streptococcus infections; Titration; Titration calorimetry; Transcription; Transduction; Zinc; Zinc compounds; United States > US
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0195746

LdtR is a master regulator of gene expression in Liberibacter asiaticus, one of the causative agents of citrus greening disease. LdtR belongs to the MarR-family of transcriptional regulators and it has been linked to the regulation of more than 180 genes in Liberibacter species, most of them gathered in the following Clusters of Orthologous Groups: cell motility, cell wall envelope, energy production, and transcription. Our previous transcriptomic evidence suggested that LdtR is directly involved in the modulation of the zinc uptake system genes (znu) in the closely related L. crescens. In this report, we show that LdtR is involved in the regulation of one of the two encoded zinc uptake mechanisms in L. asiaticus, named znu2. We also show that LdtR binds zinc with higher affinity than benzbromarone, a synthetic effector inhibitory molecule, resulting in the disruption of the LdtR:promoter interactions. Using site-directed mutagenesis, electrophoretic mobility shift assays (EMSAs), and isothermal titration calorimetry, we identified that residues C28 and T43 in LdtR, located in close proximity to the Benz1 pocket, are involved in the interaction with zinc. These results provided new evidence of a high-affinity effector molecule targeting a key player in L. asiaticus' physiology and complemented our previous findings about the mechanisms of signal transduction in members of the MarR-family.