{"title":"重氮葡萄球菌固氮酶转录激活剂NifA DNA结合域的纯化及生化性质研究。","authors":"Heidi G. Standke, Lois Kim, Cedric P. Owens","doi":"10.1007/s10930-023-10158-w","DOIUrl":null,"url":null,"abstract":"<div><p>NifA is a σ<sup>54</sup> activator that turns on bacterial nitrogen fixation under reducing conditions and when fixed cellular nitrogen levels are low. The redox sensing mechanism in NifA is poorly understood. In α- and β-proteobacteria, redox sensing involves two pairs of Cys residues within and immediately following the protein’s central AAA<sup>+</sup> domain. In this work, we examine if an additional Cys pair that is part of a C(X)<sub>5</sub> C motif and located immediately upstream of the DNA binding domain of NifA from the α-proteobacterium <i>Gluconacetobacter diazotrophicus</i> (<i>Gd</i>) is involved in redox sensing. We hypothesize that the Cys residues’ redox state may directly influence the DNA binding domain’s DNA binding affinity and/or alter the protein’s oligomeric sate. Two DNA binding domain constructs were generated, a longer construct (2C-DBD), consisting of the DNA binding domain with the upstream Cys pair, and a shorter construct (NC-DBD) that lacks the Cys pair. The <i>K</i><sub>d</sub> of NC-DBD for its cognate DNA sequence (nifH-UAS) is equal to 20.0 µM. The <i>K</i><sub>d</sub> of 2C-DBD for nifH-UAS when the Cys pair is oxidized is 34.5 µM. Reduction of the disulfide bond does not change the DNA binding affinity. Additional experiments indicate that the redox state of the Cys residues does not influence the secondary structure or oligomerization state of the NifA DNA binding domain. Together, these results demonstrate that the Cys pair upstream of the DNA binding domain of <i>Gd</i>-NifA does not regulate DNA binding or domain dimerization in a redox dependent manner.</p></div>","PeriodicalId":793,"journal":{"name":"The Protein Journal","volume":null,"pages":null},"PeriodicalIF":1.9000,"publicationDate":"2023-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10930-023-10158-w.pdf","citationCount":"0","resultStr":"{\"title\":\"Purification and Biochemical Characterization of the DNA Binding Domain of the Nitrogenase Transcriptional Activator NifA from Gluconacetobacter diazotrophicus\",\"authors\":\"Heidi G. Standke, Lois Kim, Cedric P. Owens\",\"doi\":\"10.1007/s10930-023-10158-w\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><p>NifA is a σ<sup>54</sup> activator that turns on bacterial nitrogen fixation under reducing conditions and when fixed cellular nitrogen levels are low. The redox sensing mechanism in NifA is poorly understood. In α- and β-proteobacteria, redox sensing involves two pairs of Cys residues within and immediately following the protein’s central AAA<sup>+</sup> domain. In this work, we examine if an additional Cys pair that is part of a C(X)<sub>5</sub> C motif and located immediately upstream of the DNA binding domain of NifA from the α-proteobacterium <i>Gluconacetobacter diazotrophicus</i> (<i>Gd</i>) is involved in redox sensing. We hypothesize that the Cys residues’ redox state may directly influence the DNA binding domain’s DNA binding affinity and/or alter the protein’s oligomeric sate. Two DNA binding domain constructs were generated, a longer construct (2C-DBD), consisting of the DNA binding domain with the upstream Cys pair, and a shorter construct (NC-DBD) that lacks the Cys pair. The <i>K</i><sub>d</sub> of NC-DBD for its cognate DNA sequence (nifH-UAS) is equal to 20.0 µM. The <i>K</i><sub>d</sub> of 2C-DBD for nifH-UAS when the Cys pair is oxidized is 34.5 µM. Reduction of the disulfide bond does not change the DNA binding affinity. Additional experiments indicate that the redox state of the Cys residues does not influence the secondary structure or oligomerization state of the NifA DNA binding domain. Together, these results demonstrate that the Cys pair upstream of the DNA binding domain of <i>Gd</i>-NifA does not regulate DNA binding or domain dimerization in a redox dependent manner.</p></div>\",\"PeriodicalId\":793,\"journal\":{\"name\":\"The Protein Journal\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":1.9000,\"publicationDate\":\"2023-10-03\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"https://link.springer.com/content/pdf/10.1007/s10930-023-10158-w.pdf\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"The Protein Journal\",\"FirstCategoryId\":\"2\",\"ListUrlMain\":\"https://link.springer.com/article/10.1007/s10930-023-10158-w\",\"RegionNum\":4,\"RegionCategory\":\"生物学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q4\",\"JCRName\":\"BIOCHEMISTRY & MOLECULAR BIOLOGY\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"The Protein Journal","FirstCategoryId":"2","ListUrlMain":"https://link.springer.com/article/10.1007/s10930-023-10158-w","RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q4","JCRName":"BIOCHEMISTRY & MOLECULAR BIOLOGY","Score":null,"Total":0}
Purification and Biochemical Characterization of the DNA Binding Domain of the Nitrogenase Transcriptional Activator NifA from Gluconacetobacter diazotrophicus
NifA is a σ54 activator that turns on bacterial nitrogen fixation under reducing conditions and when fixed cellular nitrogen levels are low. The redox sensing mechanism in NifA is poorly understood. In α- and β-proteobacteria, redox sensing involves two pairs of Cys residues within and immediately following the protein’s central AAA+ domain. In this work, we examine if an additional Cys pair that is part of a C(X)5 C motif and located immediately upstream of the DNA binding domain of NifA from the α-proteobacterium Gluconacetobacter diazotrophicus (Gd) is involved in redox sensing. We hypothesize that the Cys residues’ redox state may directly influence the DNA binding domain’s DNA binding affinity and/or alter the protein’s oligomeric sate. Two DNA binding domain constructs were generated, a longer construct (2C-DBD), consisting of the DNA binding domain with the upstream Cys pair, and a shorter construct (NC-DBD) that lacks the Cys pair. The Kd of NC-DBD for its cognate DNA sequence (nifH-UAS) is equal to 20.0 µM. The Kd of 2C-DBD for nifH-UAS when the Cys pair is oxidized is 34.5 µM. Reduction of the disulfide bond does not change the DNA binding affinity. Additional experiments indicate that the redox state of the Cys residues does not influence the secondary structure or oligomerization state of the NifA DNA binding domain. Together, these results demonstrate that the Cys pair upstream of the DNA binding domain of Gd-NifA does not regulate DNA binding or domain dimerization in a redox dependent manner.
期刊介绍:
The Protein Journal (formerly the Journal of Protein Chemistry) publishes original research work on all aspects of proteins and peptides. These include studies concerned with covalent or three-dimensional structure determination (X-ray, NMR, cryoEM, EPR/ESR, optical methods, etc.), computational aspects of protein structure and function, protein folding and misfolding, assembly, genetics, evolution, proteomics, molecular biology, protein engineering, protein nanotechnology, protein purification and analysis and peptide synthesis, as well as the elucidation and interpretation of the molecular bases of biological activities of proteins and peptides. We accept original research papers, reviews, mini-reviews, hypotheses, opinion papers, and letters to the editor.