Structure of the Redox Sensor Domain of Azotobacter vinelandii NifL at Atomic Resolution: Signaling, Dimerization, and Mechanism

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• 作者：Jason Key ; Marco Hefti ; Erin B. Purcell ; Keith Moffat
• 刊名：Biochemistry
• 出版年：2007
• 出版时间：March 27, 2007
• 年：2007
• 卷：46
• 期：12
• 页码：3614 - 3623
• 全文大小：597K
• 年卷期：v.46,no.12(March 27, 2007)
• ISSN：1520-4995

文摘

NifL is a multidomain sensor protein responsible for the transcriptional regulation of genesinvolved in response to changes in cellular redox state and ADP concentration. Cellular redox is monitoredby the N-terminal PAS domain of NifL which contains an FAD cofactor. Flavin-based PAS domains ofthis type have also been referred to as LOV domains. To explore the mechanism of signal recognitionand transduction in NifL, we determined the crystal structure of the FAD-bound PAS domain of NifLfrom Azotobacter vinelandii to 1.04 Å resolution. The structure reveals a novel cavity within the PASdomain which contains two water molecules directly coordinated to the FAD. This cavity is connected tosolvent by multiple access channels which may facilitate the oxidation of the FAD by molecular oxygenand the release of hydrogen peroxide. The structure contains a dimer of the NifL PAS domain that isstructurally very similar to those described in other crystal structures of PAS domains and identifies aconserved dimerization motif. An N-terminal amphipathic helix constitutes part of the dimerization interface,and similar N-terminal helices are identified in other PAS domain proteins. The structure suggests a modelfor redox-mediated signaling in which a conformational change is initiated by redox-dependent changesin protonation at the N5 atom of FAD that lead to reorganization of hydrogen bonds within the flavinbinding pocket. A structural signal is subsequently transmitted to the beta2.gif" BORDER=0 ALIGN="middle">-sheet interface between themonomers of the PAS domain.