Sakkarin BhubhanilNantaporn RuangkiattikulPhettree NiamyimJareeya ChamsingPatchara Ngok-ngamRojana SukchawalitSkorn MongkolsukApplied Biological Sciences Chulabhorn Graduate InstituteThailand Ministry of EducationChulabhorn Research InstituteEnvironmental ToxicologyMahidol University2018-06-112018-06-112012-10-01FEMS Microbiology Letters. Vol.335, No.1 (2012), 68-7715746968037810972-s2.0-84866175171https://repository.li.mahidol.ac.th/handle/20.500.14594/13607The key amino acid residues that influence the function of the Agrobacterium tumefaciens iron response regulator protein (Irr At ) were investigated. Several Irr At mutant proteins containing substitutions in amino acids corresponding to candidate metal- and haem-binding sites were constructed. The ability of the mutant proteins to repress the promoter of the membrane bound ferritin (mbfA) ge ne was investigated using a promoter-lacZ fusion assay. A single mutation at residue H94 significantly decreased the repressive activity of Irr At . Multiple mutation analysis revealed the importance of H45, H65, the HHH motif (H92, H93 and H94) and H127 for the repressor function of Irr At . H94 is essential for the iron responsiveness of Irr At . Furthermore, the Irr At mutant proteins showed differential abilities to complement the H 2 O 2 -hyper-resistant phenotype of an irr mutant. © 2012 Federation of European Microbiological Societies.Mahidol UniversityBiochemistry, Genetics and Molecular BiologyImmunology and MicrobiologyArticleSCOPUS10.1111/j.1574-6968.2012.02638.x