The LysR‐type transcription factor HbrL is a global regulator of iron homeostasis and porphyrin synthesis in Rhodobacter capsulatus

S Zappa, CE Bauer - Molecular microbiology, 2013 - Wiley Online Library
Molecular microbiology, 2013Wiley Online Library
The purple bacterium R hodobacter capsulatus is unique among R hodobacteriacae as it
contains a putative i ron r esponse r egulator (Irr) but does not possess a copy of the f erric u
ptake r egulator (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 …
Summary
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.
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