title: PpsR, a regulator of heme and bacteriochlorophyll biosynthesis, is a heme-sensing protein.
abstract: Heme-mediated regulation, presented in many biological processes, is achieved in part with proteins containing heme regulatory motif. In this study, we demonstrate that FLAG-tagged PpsR isolated from Rhodobacter sphaeroides cells contains bound heme. In vitro heme binding studies with tagless apo-PpsR show that PpsR binds heme at a near one-to-one ratio with a micromolar binding constant. Mutational and spectral assays suggest that both the second Per-Arnt-Sim (PAS) and DNA binding domains of PpsR are involved in the heme binding. Furthermore, we show that heme changes the DNA binding patterns of PpsR and induces different responses of photosystem genes expression. Thus, PpsR functions as both a redox and heme sensor to coordinate the amount of heme, bacteriochlorophyll, and photosystem apoprotein synthesis thereby providing fine tune control to avoid excess free tetrapyrrole accumulation.
authors.affiliation: Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, Indiana 47405, USA.
authors.forename: Liang
authors.initials: L
authors.lastname: Yin
authors.forename: Vladimira
authors.initials: V
authors.lastname: Dragnea
authors.forename: Carl E
authors.initials: CE
authors.lastname: Bauer
mesh_terms: D001429:Bacteriochlorophylls / Q000737:chemistry*; D004247:DNA / Q000737:chemistry*; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D003850:Deoxyribonuclease I / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism; D005786:Gene Expression Regulation; D006418:Heme / Q000737:chemistry; D007501:Iron / Q000737:chemistry; D008024:Ligands; D008968:Molecular Conformation; D010788:Photosynthesis; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D020560:Proteobacteria / Q000378:metabolism*; D012242:Rhodobacter sphaeroides / Q000378:metabolism*; D045725:Tetrapyrroles / Q000737:chemistry; D014364:Tryptophan / Q000737:chemistry
chemical_list: D001429:Bacteriochlorophylls; D004268:DNA-Binding Proteins; D008024:Ligands; D045725:Tetrapyrroles; D006418:Heme; D014364:Tryptophan; D004247:DNA; D007501:Iron; D003850:Deoxyribonuclease I