title: The LysR-type transcription factor HbrL is a global regulator of iron homeostasis and porphyrin synthesis in Rhodobacter capsulatus.
abstract: The purple bacterium Rhodobacter capsulatus is unique among Rhodobacteriacae as it contains a putative iron response regulator (Irr) but does not possess a copy of the ferric uptake regulator (Fur). Interestingly, an in-frame deletion mutant of Irr shows no major role in iron homeostasis. Instead, we showed that the previously identified activator of haem gene expression HbrL is a crucial regulator of iron homeostasis. We demonstrated that an HbrL deletion strain is unable to grow in iron-limited medium in aerobic, semi-aerobic and photosynthetic conditions and that suppressor strains can be isolated with mutations in iron uptake genes. Gene expression studies revealed that HbrL is a transcriptional activator of multiple ferrous and ferric iron uptake systems in addition to a haem uptake system. Finally, HbrL activates the expression of numerous haem biosynthesis genes. Thus, HbrL has a central role in controlling the amount of iron transport in conjunction with the synthesis of its cognate tetrapyrrole haem.
authors.affiliation: Department of Molecular and Cellular Biochemistry, Indiana University, Simon Hall, 212 S Hawthorne Dr., Bloomington, IN, 47405, USA.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Zappa
authors.forename: Carl E
authors.initials: CE
authors.lastname: Bauer
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D006418:Heme / Q000096:biosynthesis*; D006706:Homeostasis; D017136:Ion Transport / Q000235:genetics; D007501:Iron / Q000378:metabolism*; D016354:Rhodobacter capsulatus / Q000235:genetics / Q000502:physiology*; D045725:Tetrapyrroles / Q000096:biosynthesis; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D045725:Tetrapyrroles; D014157:Transcription Factors; C114259:iron response regulator protein, Bacteria; D006418:Heme; D007501:Iron