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Regulation of the phototrophic iron oxidation (pio) genes in Rhodopseudomonas palustris TIE-1 is mediated by the global regulator, FixK

Bose, Arpita and Newman, Dianne K. (2011) Regulation of the phototrophic iron oxidation (pio) genes in Rhodopseudomonas palustris TIE-1 is mediated by the global regulator, FixK. Molecular Microbiology, 79 (1). pp. 63-75. ISSN 0950-382X. http://resolver.caltech.edu/CaltechAUTHORS:20110308-123056256

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Abstract

The pioABC operon is required for phototrophic iron oxidative (photoferrotrophic) growth by the α-proteobacterium Rhodopseudomonas palustris TIE-1. Expression analysis of this operon showed that it was transcribed and translated during anaerobic growth, upregulation being observed only under photoferrotrophic conditions. Very low levels of transcription were observed during aerobic growth, suggesting expression was induced by anoxia. The presence of two canonical FixK boxes upstream of the identified pioABC transcription start site implicated FixK as a likely regulator. To test this possibility, a ΔfixK mutant of R. palustris TIE-1 was assessed for pioABC expression. pioABC expression decreased dramatically in ΔfixK versus WT during photoferrotrophic growth, implying that FixK positively regulates its expression; coincidently, the onset of iron oxidation was prolonged in this mutant. In contrast, pioABC expression increased in ΔfixK under all non-photoferrotrophic conditions tested, suggesting the presence of additional levels of regulation. Purified FixK directly bound only the proximal FixK box in gel mobility-shift assays. Mutant expression analysis revealed that FixK regulates anaerobic phototrophic expression of other target genes with FixK binding sites in their promoters. This study shows that FixK regulates key iron metabolism genes in an α-proteobacterium, pointing to a departure from the canonical Fur/Irr mode of regulation.


Item Type:Article
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http://dx.doi.org/10.1111/j.1365-2958.2010.07430.xDOIUNSPECIFIED
http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2958.2010.07430.x/abstractPublisherUNSPECIFIED
ORCID:
AuthorORCID
Newman, Dianne K.0000-0003-1647-1918
Additional Information:© 2010 Blackwell Publishing. Accepted 6 October, 2010. First published online 28 October 2010. We thank Jacob Thomas and Alan D. Grossman for providing X-ray cassettes for gel mobility-shift analysis, Graham C. Walker for providing the Kodak (CareStream) M35A X-Omat film processor and Steven K. Farrand for pSRK-Gm. A.B. is a Howard Hughes Medical Institute (HHMI) fellow of the Life Sciences Research Foundation. D.K.N. is an investigator of the HHMI. This research was supported by grants to D.K.N. from the National Science Foundation (Grant MCB-0616323) and HHMI.
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Funding AgencyGrant Number
NSFMCB-0616323
Howard Hughes Medical Institute (HHMI)UNSPECIFIED
Record Number:CaltechAUTHORS:20110308-123056256
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20110308-123056256
Official Citation:Regulation of the phototrophic iron oxidation (pio) genes in Rhodopseudomonas palustris TIE-1 is mediated by the global regulator, FixK (pages 63–75) Arpita Bose and Dianne K. Newman Article first published online: 28 OCT 2010 | DOI: 10.1111/j.1365-2958.2010.07430.x
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:22712
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:09 Mar 2011 17:03
Last Modified:24 Oct 2017 15:58

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