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The role of the GAF and central domains of the transcriptional activator VnfA in Azotobacter vinelandii
VnfA is a transcriptional activator that is required for the expression of the structural genes encoding nitrogenase‐2 in Azotobacter vinelandii. VnfA consists of three domains: an N‐terminal regulatory domain termed GAF, including a Cys‐rich motif; a central domain from the AAA+ family; and a C‐ter...
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Published in: | The FEBS journal 2011-09, Vol.278 (18), p.3287-3297 |
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Main Authors: | , , , , |
Format: | Article |
Language: | English |
Subjects: | |
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Online Access: | Get full text |
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Summary: | VnfA is a transcriptional activator that is required for the expression of the structural genes encoding nitrogenase‐2 in Azotobacter vinelandii. VnfA consists of three domains: an N‐terminal regulatory domain termed GAF, including a Cys‐rich motif; a central domain from the AAA+ family; and a C‐terminal domain for DNA binding. Previously, we reported that transcriptionally active VnfA harboring an Fe‐S cluster (presumably of the 3Fe‐4S type) as a prosthetic group and the Cys‐rich motif were possibly associated with coordination of the Fe‐S cluster. In the present study, we have investigated the roles of the GAF and central domains in the regulatory function of VnfA using truncated variants: ΔN15VnfA and ΔGAFVnfA that lack the N‐terminal 15 residues and whole GAF domain, respectively, and GAFVnfA consisting of only the GAF domain. ΔN15VnfA and ΔGAFVnfA lost the ability to bind the Fe‐S cluster, whereas GAFVnfA was still able to bind to the cluster, consistent with the hypothesis that the Cys‐rich motif is essential for Fe‐S cluster binding. The GAF domain showed an inhibitory effect on the transcriptional activity of VnfA, which was reversed in the presence of the Fe‐S cluster, and reactivated upon disassembly of the cluster. The inhibitory activity of the GAF domain acts on the NTPase activity of the central domain, whereas the binding ability of VnfA to DNA was not significantly affected, when VnfA retains its tetrameric conformation. The results imply that a major pathway, by which VnfA function is regulated, operates via the control of NTPase activity by the GAF domain.
Structured digital
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VnfA binds to VnfA by molecular sieving (View Interaction 1, 2)
Database
VnfA has been submitted to the Swiss‐Prot database under accession number: C1DI41.
VnfA is a σN‐dependent transcriptional activator required for the gene expression of nitrogenase‐2 in Azotobacter vinelandii. We found that the N‐terminal GAF domain of VnfA, which contains an Fe‐S cluster showed an inhibitory effect on the transcriptional activity of VnfA. The inhibitory effect acted on the NTPase activity of the central domain, depending on assembly and disassembly of the cluster. |
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ISSN: | 1742-464X 1742-4658 |
DOI: | 10.1111/j.1742-4658.2011.08245.x |