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Scheyer MW, Campbell C, William PL, Hussain M, Begum A, Fonseca SE, Asare IK, Dabney P, Dabney-Smith C, Lorigan GA, Sahu ID. Electron paramagnetic resonance spectroscopic characterization of the human KCNE3 protein in lipodisq nanoparticles for structural dynamics of membrane proteins. Biophys Chem 2023; 301:107080. [PMID: 37531799 DOI: 10.1016/j.bpc.2023.107080] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2023] [Revised: 07/07/2023] [Accepted: 07/24/2023] [Indexed: 08/04/2023]
Abstract
One of the major challenges in solubilization of membrane proteins is to find the optimal physiological environment for their biophysical studies. EPR spectroscopy is a powerful biophysical technique for studying the structural and dynamic properties of macromolecules. However, the challenges in the membrane protein sample preparation and flexible motion of the spin label limit the utilization of EPR spectroscopy to a majority of membrane protein systems in a physiological membrane-bound state. Recently, lipodisq nanoparticles or styrene-maleic acid copolymer-lipid nanoparticles (SMALPs) have emerged as a membrane mimetic system for investigating the structural studies of membrane proteins. However, its detail characterization for membrane protein studies is still poorly understood. Recently, we characterized the potassium channel membrane protein KCNQ1 voltage sensing domain (KCNQ1-VSD) and KCNE1 reconstituted into lipodisq nanoparticles using EPR spectroscopy. In this study, the potassium channel accessory protein KCNE3 containing flexible N- and C-termini was encapsulated into proteoliposomes and lipodisq nanoparticles and characterized for studying its structural and dynamic properties using nitroxide based site-directed spin labeling EPR spectroscopy. CW-EPR lineshape analysis data indicated an increase in spectral line broadenings with the addition of the styrene-maleic acid (SMA) polymer which approaches close to the rigid limit providing a homogeneous stabilization of the protein-lipid complex. Similarly, EPR DEER measurements indicated an enhanced quality of distance measurements with an increase in the phase memory time (Tm) values upon incorporation of the sample into lipodisq nanoparticles, when compared to proteoliposomes. These results agree with the solution NMR structural structure of the KCNE3 and EPR studies of other membrane proteins in lipodisq nanoparticles. This study along with our earlier studies will provide the reference characterization data that will provide benefit to the membrane protein researchers for studying structural dynamics of challenging membrane proteins.
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Affiliation(s)
- Matthew W Scheyer
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA
| | - Conner Campbell
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA
| | - Patrick L William
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA
| | - Mustakim Hussain
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA
| | - Afsana Begum
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA
| | | | - Isaac K Asare
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA
| | - Peyton Dabney
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA
| | - Carole Dabney-Smith
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, USA
| | - Gary A Lorigan
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, USA
| | - Indra D Sahu
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA; Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, USA.
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2
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Sarasa-Buisan C, Guío J, Peleato ML, Fillat MF, Sevilla E. Expanding the FurC (PerR) regulon in Anabaena (Nostoc) sp. PCC 7120: Genome-wide identification of novel direct targets uncovers FurC participation in central carbon metabolism regulation. PLoS One 2023; 18:e0289761. [PMID: 37549165 PMCID: PMC10406281 DOI: 10.1371/journal.pone.0289761] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Accepted: 07/25/2023] [Indexed: 08/09/2023] Open
Abstract
FurC (PerR, Peroxide Response Regulator) from Anabaena sp. PCC 7120 (also known as Nostoc sp. PCC 7120) is a master regulator engaged in the modulation of relevant processes including the response to oxidative stress, photosynthesis and nitrogen fixation. Previous differential gene expression analysis of a furC-overexpressing strain (EB2770FurC) allowed the inference of a putative FurC DNA-binding consensus sequence. In the present work, more data concerning the regulon of the FurC protein were obtained through the searching of the putative FurC-box in the whole Anabaena sp. PCC 7120 genome. The total amount of novel FurC-DNA binding sites found in the promoter regions of genes with known function was validated by electrophoretic mobility shift assays (EMSA) identifying 22 new FurC targets. Some of these identified targets display relevant roles in nitrogen fixation (hetR and hgdC) and carbon assimilation processes (cmpR, glgP1 and opcA), suggesting that FurC could be an additional player for the harmonization of carbon and nitrogen metabolisms. Moreover, differential gene expression of a selection of newly identified FurC targets was measured by Real Time RT-PCR in the furC-overexpressing strain (EB2770FurC) comparing to Anabaena sp. PCC 7120 revealing that in most of these cases FurC could act as a transcriptional activator.
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Affiliation(s)
- Cristina Sarasa-Buisan
- Departamento de Bioquímica y Biología Molecular y Celular and Institute for Biocomputation and Physics of Complex Systems, Universidad de Zaragoza, Zaragoza, Spain
| | - Jorge Guío
- Departamento de Bioquímica y Biología Molecular y Celular and Institute for Biocomputation and Physics of Complex Systems, Universidad de Zaragoza, Zaragoza, Spain
| | - M. Luisa Peleato
- Departamento de Bioquímica y Biología Molecular y Celular and Institute for Biocomputation and Physics of Complex Systems, Universidad de Zaragoza, Zaragoza, Spain
| | - María F. Fillat
- Departamento de Bioquímica y Biología Molecular y Celular and Institute for Biocomputation and Physics of Complex Systems, Universidad de Zaragoza, Zaragoza, Spain
| | - Emma Sevilla
- Departamento de Bioquímica y Biología Molecular y Celular and Institute for Biocomputation and Physics of Complex Systems, Universidad de Zaragoza, Zaragoza, Spain
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3
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Xu X, Rachedi R, Foglino M, Talla E, Latifi A. Interaction network among factors involved in heterocyst-patterning in cyanobacteria. Mol Genet Genomics 2022; 297:999-1015. [PMID: 35577979 DOI: 10.1007/s00438-022-01902-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2021] [Accepted: 04/16/2022] [Indexed: 10/18/2022]
Abstract
The genetically regulated pattern of heterocyst formation in multicellular cyanobacteria represents the simplest model to address how patterns emerge and are established, the signals that control them, and the regulatory pathways that act downstream. Although numerous factors involved in this process have been identified, the mechanisms of action of many of them remain largely unknown. The aim of this study was to identify specific relationships between 14 factors required for cell differentiation and pattern formation by exploring their putative physical interactions in the cyanobacterium model Nostoc sp. PCC 7120 and by probing their evolutionary conservation and distribution across the cyanobacterial phylum. A bacterial two-hybrid assay indicated that 10 of the 14 factors studied here are engaged in more than one protein-protein interaction. The transcriptional regulator PatB was central in this network as it showed the highest number of binary interactions. A phylum-wide genomic survey of the distribution of these factors in cyanobacteria showed that they are all highly conserved in the genomes of heterocyst-forming strains, with the PatN protein being almost restricted to this clade. Interestingly, eight of the factors that were shown to be capable of protein interactions were identified as key elements in the evolutionary genomics analysis. These data suggest that a network of 12 proteins may play a crucial role in heterocyst development and patterning. Unraveling the physical and functional interactions between these factors during heterocyst development will certainly shed light on the mechanisms underlying pattern establishment in cyanobacteria.
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Affiliation(s)
- Xiaomei Xu
- Aix-Marseille University, CNRS, IMM, LCB, Laboratoire de Chimie Bactérienne, France, Marseille
| | - Raphaël Rachedi
- Aix-Marseille University, CNRS, IMM, LCB, Laboratoire de Chimie Bactérienne, France, Marseille
| | - Maryline Foglino
- Aix-Marseille University, CNRS, IMM, LCB, Laboratoire de Chimie Bactérienne, France, Marseille
| | - Emmanuel Talla
- Aix-Marseille University, CNRS, IMM, LCB, Laboratoire de Chimie Bactérienne, France, Marseille.
| | - Amel Latifi
- Aix-Marseille University, CNRS, IMM, LCB, Laboratoire de Chimie Bactérienne, France, Marseille.
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4
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Sarasa-Buisan C, Guio J, Broset E, Peleato ML, Fillat MF, Sevilla E. FurC (PerR) from Anabaena sp. PCC7120: a versatile transcriptional regulator engaged in the regulatory network of heterocyst development and nitrogen fixation. Environ Microbiol 2021; 24:566-582. [PMID: 33938105 DOI: 10.1111/1462-2920.15552] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Revised: 04/19/2021] [Accepted: 04/30/2021] [Indexed: 11/29/2022]
Abstract
FurC (PerR) from Anabaena sp. PCC7120 was previously described as a key transcriptional regulator involved in setting off the oxidative stress response. In the last years, the cross-talk between oxidative stress, iron homeostasis and nitrogen metabolism is becoming more and more evident. In this work, the transcriptome of a furC-overexpressing strain was compared with that of a wild-type strain under both standard and nitrogen-deficiency conditions. The results showed that the overexpression of furC deregulates genes involved in several categories standing out photosynthesis, iron transport and nitrogen metabolism. The novel FurC-direct targets included some regulatory elements that control heterocyst development (hetZ and asr1734), genes directly involved in the heterocyst envelope formation (devBCA and hepC) and genes which participate in the nitrogen fixation process (nifHDK and nifH2, rbrA rubrerythrin and xisHI excisionase). Likewise, furC overexpression notably impacts the mRNA levels of patA encoding a key protein in the heterocyst pattern formation. The relevance of FurC in these processes is bringing out by the fact that the overexpression of furC impairs heterocyst development and cell growth under nitrogen step-down conditions. In summary, this work reveals a new player in the complex regulatory network of heterocyst formation and nitrogen fixation.
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Affiliation(s)
- Cristina Sarasa-Buisan
- Departamento de Bioquímica y Biología Molecular y Celular and Institute for Biocomputation and Physics of Complex Systems, Universidad de Zaragoza, Pedro Cerbuna 12, Zaragoza, 50009, Spain
| | - Jorge Guio
- Departamento de Bioquímica y Biología Molecular y Celular and Institute for Biocomputation and Physics of Complex Systems, Universidad de Zaragoza, Pedro Cerbuna 12, Zaragoza, 50009, Spain
| | - Esther Broset
- Departamento de Bioquímica y Biología Molecular y Celular and Institute for Biocomputation and Physics of Complex Systems, Universidad de Zaragoza, Pedro Cerbuna 12, Zaragoza, 50009, Spain
| | - M Luisa Peleato
- Departamento de Bioquímica y Biología Molecular y Celular and Institute for Biocomputation and Physics of Complex Systems, Universidad de Zaragoza, Pedro Cerbuna 12, Zaragoza, 50009, Spain
| | - María F Fillat
- Departamento de Bioquímica y Biología Molecular y Celular and Institute for Biocomputation and Physics of Complex Systems, Universidad de Zaragoza, Pedro Cerbuna 12, Zaragoza, 50009, Spain
| | - Emma Sevilla
- Departamento de Bioquímica y Biología Molecular y Celular and Institute for Biocomputation and Physics of Complex Systems, Universidad de Zaragoza, Pedro Cerbuna 12, Zaragoza, 50009, Spain
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5
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Xu X, Risoul V, Byrne D, Champ S, Douzi B, Latifi A. HetL, HetR and PatS form a reaction-diffusion system to control pattern formation in the cyanobacterium nostoc PCC 7120. eLife 2020; 9:e59190. [PMID: 32762845 PMCID: PMC7476756 DOI: 10.7554/elife.59190] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2020] [Accepted: 08/06/2020] [Indexed: 11/13/2022] Open
Abstract
Local activation and long-range inhibition are mechanisms conserved in self-organizing systems leading to biological patterns. A number of them involve the production by the developing cell of an inhibitory morphogen, but how this cell becomes immune to self-inhibition is rather unknown. Under combined nitrogen starvation, the multicellular cyanobacterium Nostoc PCC 7120 develops nitrogen-fixing heterocysts with a pattern of one heterocyst every 10-12 vegetative cells. Cell differentiation is regulated by HetR which activates the synthesis of its own inhibitory morphogens, diffusion of which establishes the differentiation pattern. Here, we show that HetR interacts with HetL at the same interface as PatS, and that this interaction is necessary to suppress inhibition and to differentiate heterocysts. hetL expression is induced under nitrogen-starvation and is activated by HetR, suggesting that HetL provides immunity to the heterocyst. This protective mechanism might be conserved in other differentiating cyanobacteria as HetL homologues are spread across the phylum.
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Affiliation(s)
- Xiaomei Xu
- Aix Marseille Univ, CNRS, LCB, Laboratoire de Chimie BactérienneMarseilleFrance
| | - Véronique Risoul
- Aix Marseille Univ, CNRS, LCB, Laboratoire de Chimie BactérienneMarseilleFrance
| | - Deborah Byrne
- Aix Marseille Univ, CNRS, Protein Expression Facility, Institut de Microbiologie de la MéditerranéeMarseilleFrance
| | - Stéphanie Champ
- Aix Marseille Univ, CNRS, LCB, Laboratoire de Chimie BactérienneMarseilleFrance
| | | | - Amel Latifi
- Aix Marseille Univ, CNRS, LCB, Laboratoire de Chimie BactérienneMarseilleFrance
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6
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Sahu ID, Dixit G, Reynolds WD, Kaplevatsky R, Harding BD, Jaycox CK, McCarrick RM, Lorigan GA. Characterization of the Human KCNQ1 Voltage Sensing Domain (VSD) in Lipodisq Nanoparticles for Electron Paramagnetic Resonance (EPR) Spectroscopic Studies of Membrane Proteins. J Phys Chem B 2020; 124:2331-2342. [PMID: 32130007 DOI: 10.1021/acs.jpcb.9b11506] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Membrane proteins are responsible for conducting essential biological functions that are necessary for the survival of living organisms. In spite of their physiological importance, limited structural information is currently available as a result of challenges in applying biophysical techniques for studying these protein systems. Electron paramagnetic resonance (EPR) spectroscopy is a very powerful technique to study the structural and dynamic properties of membrane proteins. However, the application of EPR spectroscopy to membrane proteins in a native membrane-bound state is extremely challenging due to the complexity observed in inhomogeneity sample preparation and the dynamic motion of the spin label. Detergent micelles are very popular membrane mimetics for membrane proteins due to their smaller size and homogeneity, providing high-resolution structure analysis by solution NMR spectroscopy. However, it is important to test whether the protein structure in a micelle environment is the same as that of its membrane-bound state. Lipodisq nanoparticles or styrene-maleic acid copolymer-lipid nanoparticles (SMALPs) have been introduced as a potentially good membrane-mimetic system for structural studies of membrane proteins. Recently, we reported on the EPR characterization of the KCNE1 membrane protein having a single transmembrane incorporated into lipodisq nanoparticles. In this work, lipodisq nanoparticles were used as a membrane mimic system for probing the structural and dynamic properties of the more complicated membrane protein system human KCNQ1 voltage sensing domain (Q1-VSD) having four transmembrane helices using site-directed spin-labeling EPR spectroscopy. Characterization of spin-labeled Q1-VSD incorporated into lipodisq nanoparticles was carried out using CW-EPR spectral line shape analysis and pulsed EPR double-electron electron resonance (DEER) measurements. The CW-EPR spectra indicate an increase in spectral line broadening with the addition of the styrene-maleic acid (SMA) polymer which approaches close to the rigid limit providing a homogeneous stabilization of the protein-lipid complex. Similarly, EPR DEER measurements indicated a superior quality of distance measurement with an increase in the phase memory time (Tm) values upon incorporation of the sample into lipodisq nanoparticles when compared to proteoliposomes. These results are consistent with the solution NMR structural studies on the Q1-VSD. This study will be beneficial for researchers working on investigating the structural and dynamic properties of more complicated membrane protein systems using lipodisq nanoparticles.
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Affiliation(s)
- Indra D Sahu
- Department of Chemistry and Biochemistry, Miami University, Oxford, Ohio 45056, United States.,Natural Science Division, Campbellsville University, Campbellsville, Kentucky 42718, United States
| | - Gunjan Dixit
- Department of Chemistry and Biochemistry, Miami University, Oxford, Ohio 45056, United States
| | - Warren D Reynolds
- Department of Chemistry and Biochemistry, Miami University, Oxford, Ohio 45056, United States
| | - Ryan Kaplevatsky
- Department of Chemistry and Biochemistry, Miami University, Oxford, Ohio 45056, United States
| | - Benjamin D Harding
- Department of Chemistry and Biochemistry, Miami University, Oxford, Ohio 45056, United States
| | - Colleen K Jaycox
- Department of Chemistry and Biochemistry, Miami University, Oxford, Ohio 45056, United States
| | - Robert M McCarrick
- Department of Chemistry and Biochemistry, Miami University, Oxford, Ohio 45056, United States
| | - Gary A Lorigan
- Department of Chemistry and Biochemistry, Miami University, Oxford, Ohio 45056, United States
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7
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Flores E, Picossi S, Valladares A, Herrero A. Transcriptional regulation of development in heterocyst-forming cyanobacteria. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2019; 1862:673-684. [DOI: 10.1016/j.bbagrm.2018.04.006] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2018] [Revised: 04/27/2018] [Accepted: 04/27/2018] [Indexed: 01/02/2023]
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8
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Elhai J, Khudyakov I. Ancient association of cyanobacterial multicellularity with the regulator HetR and an RGSGR pentapeptide-containing protein (PatX). Mol Microbiol 2018; 110:931-954. [PMID: 29885033 DOI: 10.1111/mmi.14003] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/04/2018] [Indexed: 12/14/2022]
Abstract
One simple model to explain biological pattern postulates the existence of a stationary regulator of differentiation that positively affects its own expression, coupled with a diffusible suppressor of differentiation that inhibits the regulator's expression. The first has been identified in the filamentous, heterocyst-forming cyanobacterium, Anabaena PCC 7120 as the transcriptional regulator, HetR and the second as the small protein, PatS, which contains a critical RGSGR motif that binds to HetR. HetR is present in almost all filamentous cyanobacteria, but only a subset of heterocyst-forming strains carry proteins similar to PatS. We identified a third protein, PatX that also carries the RGSGR motif and is coextensive with HetR. Amino acid sequences of PatX contain two conserved regions: the RGSGR motif and a hydrophobic N-terminus. Within 69 nt upstream from all instances of the gene is a DIF1 motif correlated in Anabaena with promoter induction in developing heterocysts, preceded in heterocyst-forming strains by an apparent NtcA-binding site, associated with regulation by nitrogen-status. Consistent with a role in the simple model, PatX is expressed dependent on HetR and acts to inhibit differentiation. The acquisition of the PatX/HetR pair preceded the appearance of both PatS and heterocysts, dating back to the beginnings of multicellularity.
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Affiliation(s)
- Jeff Elhai
- Center for the Study of Biological Complexity, Virginia Commonwealth University, Richmond, VA, 23284, USA
| | - Ivan Khudyakov
- All-Russia Research Institute for Agricultural Microbiology, Saint-Petersburg, 196608, Russia
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9
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Herrero A, Flores E. Genetic responses to carbon and nitrogen availability in Anabaena. Environ Microbiol 2018; 21:1-17. [PMID: 30066380 DOI: 10.1111/1462-2920.14370] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2018] [Revised: 07/27/2018] [Accepted: 07/29/2018] [Indexed: 11/27/2022]
Abstract
Heterocyst-forming cyanobacteria are filamentous organisms that perform oxygenic photosynthesis and CO2 fixation in vegetative cells and nitrogen fixation in heterocysts, which are formed under deprivation of combined nitrogen. These organisms can acclimate to use different sources of nitrogen and respond to different levels of CO2 . Following work mainly done with the best studied heterocyst-forming cyanobacterium, Anabaena, here we summarize the mechanisms of assimilation of ammonium, nitrate, urea and N2 , the latter involving heterocyst differentiation, and describe aspects of CO2 assimilation that involves a carbon concentration mechanism. These processes are subjected to regulation establishing a hierarchy in the assimilation of nitrogen sources -with preference for the most reduced nitrogen forms- and a dependence on sufficient carbon. This regulation largely takes place at the level of gene expression and is exerted by a variety of transcription factors, including global and pathway-specific transcriptional regulators. NtcA is a CRP-family protein that adjusts global gene expression in response to the C-to-N balance in the cells, and PacR is a LysR-family transcriptional regulator (LTTR) that extensively acclimates the cells to oxygenic phototrophy. A cyanobacterial-specific transcription factor, HetR, is involved in heterocyst differentiation, and other LTTR factors are specifically involved in nitrate and CO2 assimilation.
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Affiliation(s)
- Antonia Herrero
- Instituto de Bioquímica Vegetal y Fotosíntesis, CSIC and Universidad de Sevilla, Américo Vespucio 49, E-41092, Seville, Spain
| | - Enrique Flores
- Instituto de Bioquímica Vegetal y Fotosíntesis, CSIC and Universidad de Sevilla, Américo Vespucio 49, E-41092, Seville, Spain
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10
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Rivers OS, Beurmann S, Dow A, Cozy LM, Videau P. Phenotypic Assessment Suggests Multiple Start Codons for HetN, an Inhibitor of Heterocyst Differentiation, in Anabaena sp. Strain PCC 7120. J Bacteriol 2018; 200:e00220-18. [PMID: 29784882 PMCID: PMC6060353 DOI: 10.1128/jb.00220-18] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Accepted: 05/14/2018] [Indexed: 11/20/2022] Open
Abstract
Multicellular organisms must carefully regulate the timing, number, and location of specialized cellular development. In the filamentous cyanobacterium Anabaena sp. strain PCC 7120, nitrogen-fixing heterocysts are interspersed between vegetative cells in a periodic pattern to achieve an optimal exchange of bioavailable nitrogen and reduced carbon. The spacing between heterocysts is regulated by the activity of two developmental inhibitors, PatS and HetN. PatS functions to create a de novo pattern from a homogenous field of undifferentiated cells, while HetN maintains the pattern throughout subsequent growth. Both PatS and HetN harbor the peptide motif ERGSGR, which is sufficient to inhibit development. While the small size of PatS makes the interpretation of inhibitory domains relatively simple, HetN is a 287-amino-acid protein with multiple functional regions. Previous work suggested the possibility of a truncated form of HetN containing the ERGSGR motif as the source of the HetN-derived inhibitory signal. In this work, we present evidence that the glutamate of the ERGSGR motif is required for proper HetN inhibition of heterocysts. Mutational analysis and subcellular localization indicate that the gene encoding HetN uses two methionine start codons (M1 and M119) to encode two protein forms: M1 is required for protein localization, while M119 is primarily responsible for inhibitory function. Finally, we demonstrate that patS and hetN are not functionally equivalent when expressed from the other gene's regulatory sequences. Taken together, these results help clarify the functional forms of HetN and will help refine future work defining a HetN-derived inhibitory signal in this model of one-dimensional periodic patterning.IMPORTANCE The proper placement of different cell types during a developmental program requires the creation and maintenance of a biological pattern to define the cells that will differentiate. Here we show that the HetN inhibitor, responsible for pattern maintenance of specialized nitrogen-fixing heterocyst cells in the filamentous cyanobacterium Anabaena, may be produced from two different start methionine codons. This work demonstrates that the two start sites are individually involved in a different HetN function, either membrane localization or inhibition of cellular differentiation.
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Affiliation(s)
- Orion S Rivers
- University of Hawaii at Manoa, Department of Microbiology, Honolulu, Hawaii, USA
| | - Silvia Beurmann
- University of Maryland, Institute for Genome Sciences, Maryland School of Medicine, Baltimore, Maryland, USA
| | - Allexa Dow
- University of Hawaii at Manoa, Department of Microbiology, Honolulu, Hawaii, USA
| | - Loralyn M Cozy
- Illinois Wesleyan University, Department of Biology, Bloomington, Illinois, USA
| | - Patrick Videau
- Dakota State University, Biology Department, College of Arts and Sciences, Madison, South Dakota
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11
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Li Z, Munro K, Narouz MR, Lau A, Hao H, Crudden CM, Horton JH. Self-Assembled N-Heterocyclic Carbene-Based Carboxymethylated Dextran Monolayers on Gold as a Tunable Platform for Designing Affinity-Capture Biosensor Surfaces. ACS APPLIED MATERIALS & INTERFACES 2018; 10:17560-17570. [PMID: 29741868 DOI: 10.1021/acsami.8b02595] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Sensor surfaces play a predominant role in the development of optical biosensor technologies for the analysis of biomolecular interactions. Thiol-based self-assembled monolayers (SAMs) on gold have been widely used as linker layers for sensor surfaces. However, the degradation of the thiol-gold bond can limit the performance and durability of such surfaces, directly impacting their performance and cost-effectiveness. To this end, a new family of materials based on N-heterocyclic carbenes (NHCs) has emerged as an alternative for surface modification, capable of self-assembling onto a gold surface with higher affinity and superior stability as compared to the thiol-based systems. Here we demonstrate three applications of NHC SAMs supporting a dextran layer as a tunable platform for developing various affinity-capture biosensor surfaces. We describe the development and testing of NHC-based dextran biosensor surfaces modified with each of streptavidin, nitrilotriacetic acid, and recombinant Protein A. These affinity-capture sensor surfaces enable oriented binding of ligands for optimal performance in biomolecular assays. Together, the intrinsic high stability and flexible design of the NHC biosensing platforms show great promise and open up exciting possibilities for future biosensing applications.
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Affiliation(s)
| | | | | | | | - Hongxia Hao
- Collaborative Innovation Center of Judicial Civilization and Key Laboratory of Evidence Science , China University of Political Science and Law , Beijing 100088 , China
| | - Cathleen M Crudden
- Institute for Transformative Bio-Molecules (ITbM-WPI) , Nagoya University , Chikusa, Nagoya 464-8602 , Japan
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12
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Di Patti F, Lavacchi L, Arbel-Goren R, Schein-Lubomirsky L, Fanelli D, Stavans J. Robust stochastic Turing patterns in the development of a one-dimensional cyanobacterial organism. PLoS Biol 2018; 16:e2004877. [PMID: 29727442 PMCID: PMC5955598 DOI: 10.1371/journal.pbio.2004877] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Revised: 05/16/2018] [Accepted: 04/05/2018] [Indexed: 12/25/2022] Open
Abstract
Under nitrogen deprivation, the one-dimensional cyanobacterial organism Anabaena sp. PCC 7120 develops patterns of single, nitrogen-fixing cells separated by nearly regular intervals of photosynthetic vegetative cells. We study a minimal, stochastic model of developmental patterns in Anabaena that includes a nondiffusing activator, two diffusing inhibitor morphogens, demographic fluctuations in the number of morphogen molecules, and filament growth. By tracking developing filaments, we provide experimental evidence for different spatiotemporal roles of the two inhibitors during pattern maintenance and for small molecular copy numbers, justifying a stochastic approach. In the deterministic limit, the model yields Turing patterns within a region of parameter space that shrinks markedly as the inhibitor diffusivities become equal. Transient, noise-driven, stochastic Turing patterns are produced outside this region, which can then be fixed by downstream genetic commitment pathways, dramatically enhancing the robustness of pattern formation, also in the biologically relevant situation in which the inhibitors' diffusivities may be comparable.
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Affiliation(s)
- Francesca Di Patti
- Università degli Studi di Firenze, Dipartimento di Fisica e Astronomia, Sesto Fiorentino, Italia
- CSDC and INFN Sez.di Firenze, Sesto Fiorentino, Italia
| | - Laura Lavacchi
- Università degli Studi di Firenze, Dipartimento di Fisica e Astronomia, Sesto Fiorentino, Italia
| | - Rinat Arbel-Goren
- Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot, Israel
| | | | - Duccio Fanelli
- Università degli Studi di Firenze, Dipartimento di Fisica e Astronomia, Sesto Fiorentino, Italia
- CSDC and INFN Sez.di Firenze, Sesto Fiorentino, Italia
| | - Joel Stavans
- Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot, Israel
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13
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Antonaru LA, Nürnberg DJ. Role of PatS and cell type on the heterocyst spacing pattern in a filamentous branching cyanobacterium. FEMS Microbiol Lett 2017; 364:3983256. [PMID: 28859320 PMCID: PMC5812504 DOI: 10.1093/femsle/fnx154] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2017] [Accepted: 07/19/2017] [Indexed: 12/16/2022] Open
Abstract
Cell differentiation is one of the marks of multicellular organisms. Terminally specialised nitrogen-fixing cells, termed heterocysts, evolved in filamentous cyanobacteria more than 2 Gya. The development of their spacing pattern has been thoroughly investigated in model organisms such as Anabaena sp. PCC 7120. This paper focuses on the more complex, branching cyanobacterium Mastigocladus laminosus (Stigonematales). Contrary to what has been previously published, a heterocyst spacing pattern is present in M. laminosus but it varies with the age of the culture and the morphology of the cells. Heterocysts in young, narrow trichomes were more widely spaced (∼14.8 cells) than those in old, wide trichomes (∼9.4 cells). Biochemical and transgenic experiments reveal that the heterocyst spacing pattern is affected by the heterocyst inhibitor PatS. Addition of the pentapeptide RGSGR (PatS-5) to the growth medium and overexpression of patS from Anabaena sp. PCC 7120 in M. laminosus resulted in the loss of heterocyst differentiation under nitrogen deprivation. Bioinformatics investigations indicated that putative PatS sequences within cyanobacteria are highly diverse, and fall into two main clades. Both are present in most branching cyanobacteria. Despite its more complex, branching phenotype, M. laminosus appears to use a PatS-based pathway for heterocyst differentiation, a property shared by Anabaena/Nostoc.
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14
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Mariscal V, Nürnberg DJ, Herrero A, Mullineaux CW, Flores E. Overexpression of SepJ alters septal morphology and heterocyst pattern regulated by diffusible signals in Anabaena. Mol Microbiol 2016; 101:968-81. [PMID: 27273832 DOI: 10.1111/mmi.13436] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Revised: 06/02/2016] [Indexed: 01/08/2023]
Abstract
Filamentous, N2 -fixing, heterocyst-forming cyanobacteria grow as chains of cells that are connected by septal junctions. In the model organism Anabaena sp. strain PCC 7120, the septal protein SepJ is required for filament integrity, normal intercellular molecular exchange, heterocyst differentiation, and diazotrophic growth. An Anabaena strain overexpressing SepJ made wider septa between vegetative cells than the wild type, which correlated with a more spread location of SepJ in the septa as observed with a SepJ-GFP fusion, and contained an increased number of nanopores, the septal peptidoglycan perforations that likely accommodate septal junctions. The septa between heterocysts and vegetative cells, which are narrow in wild-type Anabaena, were notably enlarged in the SepJ-overexpressing mutant. Intercellular molecular exchange tested with fluorescent tracers was increased for the SepJ-overexpressing strain specifically in the case of calcein transfer between vegetative cells and heterocysts. These results support an association between calcein transfer, SepJ-related septal junctions, and septal peptidoglycan nanopores. Under nitrogen deprivation, the SepJ-overexpressing strain produced an increased number of contiguous heterocysts but a decreased percentage of total heterocysts. These effects were lost or altered in patS and hetN mutant backgrounds, supporting a role of SepJ in the intercellular transfer of regulatory signals for heterocyst differentiation.
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Affiliation(s)
- Vicente Mariscal
- Instituto de Bioquímica Vegetal y Fotosíntesis, Consejo Superior de Investigaciones Científicas and Universidad de Sevilla, Américo Vespucio 49, Seville, E-41092, Spain
| | - Dennis J Nürnberg
- School of Biological and Chemical Sciences, Queen Mary University of London, London, E1 4NS, UK
| | - Antonia Herrero
- Instituto de Bioquímica Vegetal y Fotosíntesis, Consejo Superior de Investigaciones Científicas and Universidad de Sevilla, Américo Vespucio 49, Seville, E-41092, Spain
| | - Conrad W Mullineaux
- School of Biological and Chemical Sciences, Queen Mary University of London, London, E1 4NS, UK
| | - Enrique Flores
- Instituto de Bioquímica Vegetal y Fotosíntesis, Consejo Superior de Investigaciones Científicas and Universidad de Sevilla, Américo Vespucio 49, Seville, E-41092, Spain.
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15
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Formation and maintenance of nitrogen-fixing cell patterns in filamentous cyanobacteria. Proc Natl Acad Sci U S A 2016; 113:6218-23. [PMID: 27162328 DOI: 10.1073/pnas.1524383113] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Cyanobacteria forming one-dimensional filaments are paradigmatic model organisms of the transition between unicellular and multicellular living forms. Under nitrogen-limiting conditions, in filaments of the genus Anabaena, some cells differentiate into heterocysts, which lose the possibility to divide but are able to fix environmental nitrogen for the colony. These heterocysts form a quasiregular pattern in the filament, representing a prototype of patterning and morphogenesis in prokaryotes. Recent years have seen advances in the identification of the molecular mechanism regulating this pattern. We use these data to build a theory on heterocyst pattern formation, for which both genetic regulation and the effects of cell division and filament growth are key components. The theory is based on the interplay of three generic mechanisms: local autoactivation, early long-range inhibition, and late long-range inhibition. These mechanisms can be identified with the dynamics of hetR, patS, and hetN expression. Our theory reproduces quantitatively the experimental dynamics of pattern formation and maintenance for wild type and mutants. We find that hetN alone is not enough to play the role as the late inhibitory mechanism: a second mechanism, hypothetically the products of nitrogen fixation supplied by heterocysts, must also play a role in late long-range inhibition. The preponderance of even intervals between heterocysts arises naturally as a result of the interplay between the timescales of genetic regulation and cell division. We also find that a purely stochastic initiation of the pattern, without a two-stage process, is enough to reproduce experimental observations.
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16
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Mutation of the murC and murB Genes Impairs Heterocyst Differentiation in Anabaena sp. Strain PCC 7120. J Bacteriol 2016; 198:1196-206. [PMID: 26811320 DOI: 10.1128/jb.01027-15] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2015] [Accepted: 01/20/2016] [Indexed: 01/04/2023] Open
Abstract
UNLABELLED To stabilize cellular integrity in the face of environmental perturbations, most bacteria, including cyanobacteria, synthesize and maintain a strong, flexible, three-dimensional peptidoglycan lattice. Anabaena sp. strain PCC 7120 is a filamentous cyanobacterium capable of differentiating morphologically distinct nitrogen-fixing heterocyst cells in a periodic pattern. While heterocyst development has been shown to require proper peptidoglycan remodeling, the role of peptidoglycan synthesis has remained unclear. Here we report the identification of two peptidoglycan synthesis genes, murC (alr5065) and murB (alr5066), as required for heterocyst development. The murC and murB genes are predicted to encode a UDP-N-acetylmuramate:L-alanine ligase and a UDP-N-acetylenolpyruvoylglucosamine reductase, respectively, and we confirm enzymatic function through complementation of Escherichia coli strains deficient for these enzymes. Cells depleted of either murC or murB expression failed to differentiate heterocysts under normally inducing conditions and displayed decreased filament integrity. To identify the stage(s) of development affected by murC or murB depletion, the spatial distribution of expression of the patterning marker gene, patS, was examined. Whereas murB depletion did not affect the pattern of patS expression, murC depletion led to aberrant expression of patS in all cells of the filament. Finally, expression of gfp controlled by the region of DNA immediately upstream of murC was enriched in differentiating cells and was repressed by the transcription factor NtcA. Collectively, the data in this work provide evidence for a direct link between peptidoglycan synthesis and the maintenance of a biological pattern in a multicellular organism. IMPORTANCE Multicellular organisms that differentiate specialized cells must regulate morphological changes such that both cellular integrity and the dissemination of developmental signals are preserved. Here we show that the multicellular bacterium Anabaena, which differentiates a periodic pattern of specialized heterocyst cells, requires peptidoglycan synthesis by the murine ligase genes murC (alr5065) and murB (alr5066) for maintenance of patterned gene expression, filament integrity, and overall development. This work highlights the significant influence that intracellular structure and intercellular connections can have on the execution of a developmental program.
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17
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Valladares A, Flores E, Herrero A. The heterocyst differentiation transcriptional regulator HetR of the filamentous cyanobacteriumAnabaenaforms tetramers and can be regulated by phosphorylation. Mol Microbiol 2015; 99:808-19. [DOI: 10.1111/mmi.13268] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/06/2015] [Indexed: 11/29/2022]
Affiliation(s)
- Ana Valladares
- Instituto de Bioquímica Vegetal y Fotosíntesis; Consejo Superior de Investigaciones Científicas; Universidad de Sevilla; Américo Vespucio 49 E-41092 Seville Spain
| | - Enrique Flores
- Instituto de Bioquímica Vegetal y Fotosíntesis; Consejo Superior de Investigaciones Científicas; Universidad de Sevilla; Américo Vespucio 49 E-41092 Seville Spain
| | - Antonia Herrero
- Instituto de Bioquímica Vegetal y Fotosíntesis; Consejo Superior de Investigaciones Científicas; Universidad de Sevilla; Américo Vespucio 49 E-41092 Seville Spain
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18
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Structural insights into HetR-PatS interaction involved in cyanobacterial pattern formation. Sci Rep 2015; 5:16470. [PMID: 26576507 PMCID: PMC4649674 DOI: 10.1038/srep16470] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Accepted: 10/12/2015] [Indexed: 01/07/2023] Open
Abstract
The one-dimensional pattern of heterocyst in the model cyanobacterium Anabaena sp. PCC 7120 is coordinated by the transcription factor HetR and PatS peptide. Here we report the complex structures of HetR binding to DNA, and its hood domain (HetRHood) binding to a PatS-derived hexapeptide (PatS6) at 2.80 and 2.10 Å, respectively. The intertwined HetR dimer possesses a couple of novel HTH motifs, each of which consists of two canonical α-helices in the DNA-binding domain and an auxiliary α-helix from the flap domain of the neighboring subunit. Two PatS6 peptides bind to the lateral clefts of HetRHood, and trigger significant conformational changes of the flap domain, resulting in dissociation of the auxiliary α-helix and eventually release of HetR from the DNA major grove. These findings provide the structural insights into a prokaryotic example of Turing model.
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19
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ABC Transporter Required for Intercellular Transfer of Developmental Signals in a Heterocystous Cyanobacterium. J Bacteriol 2015; 197:2685-93. [PMID: 26055115 DOI: 10.1128/jb.00304-15] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2015] [Accepted: 06/03/2015] [Indexed: 01/20/2023] Open
Abstract
UNLABELLED In the filamentous cyanobacterium Anabaena, patS and hetN encode peptide-derived signals with many of the properties of morphogens. These signals regulate the formation of a periodic pattern of heterocysts by lateral inhibition of differentiation. Here we show that intercellular transfer of the patS- and hetN-dependent developmental signals from heterocysts to vegetative cells requires HetC, a predicted ATP-binding cassette transporter (ABC transporter). Relative to the wild type, in a hetC mutant differentiation resulted in a reduced number of heterocysts that were incapable of nitrogen fixation, but deletion of patS or hetN restored heterocyst number and function in a hetC background. These epistasis results suggest that HetC is necessary for conferring self-immunity to the inhibitors on differentiating cells. Nine hours after induction of differentiation, HetC was required for neither induction of transcription of patS nor intercellular transfer of the patS-encoded signal to neighboring cells. Conversely, in strains lacking HetC, the patS- and hetN-encoded signals were not transferred from heterocyst cells to adjacent vegetative cells. The results support a model in which the patS-dependent signal is initially transferred between vegetative cells in a HetC-independent fashion, but some time before morphological differentiation of heterocysts is complete, transfer of both signals transitions to a HetC-dependent process. IMPORTANCE How chemical cues that regulate pattern formation in multicellular organisms move from one cell to another is a central question in developmental biology. In this study, we show that an ABC transporter, HetC, is necessary for transport of two developmental signals between different types of cells in a filamentous cyanobacterium. ABC transporters are found in organisms as diverse as bacteria and humans and, as the name implies, are often involved in the transport of molecules across a cellular membrane. The activity of HetC was shown to be required for signaling between heterocysts, which supply fixed nitrogen to the organism, and other cells, as well as for conferring immunity to self-signaling on developing heterocysts.
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20
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Aitha M, Moritz L, Sahu ID, Sanyurah O, Roche Z, McCarrick R, Lorigan GA, Bennett B, Crowder MW. Conformational dynamics of metallo-β-lactamase CcrA during catalysis investigated by using DEER spectroscopy. J Biol Inorg Chem 2015; 20:585-94. [PMID: 25827593 PMCID: PMC4733638 DOI: 10.1007/s00775-015-1244-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2014] [Accepted: 01/26/2015] [Indexed: 10/24/2022]
Abstract
Previous crystallographic and mutagenesis studies have implicated the role of a position-conserved hairpin loop in the metallo-β-lactamases in substrate binding and catalysis. In an effort to probe the motion of that loop during catalysis, rapid-freeze-quench double electron-electron resonance (RFQ-DEER) spectroscopy was used to interrogate metallo-β-lactamase CcrA, which had a spin label at position 49 on the loop and spin labels (at positions 82, 126, or 233) 20-35 Å away from residue 49, during catalysis. At 10 ms after mixing, the DEER spectra show distance increases of 7, 10, and 13 Å between the spin label at position 49 and the spin labels at positions 82, 126, and 233, respectively. In contrast to previous hypotheses, these data suggest that the loop moves nearly 10 Å away from the metal center during catalysis and that the loop does not clamp down on the substrate during catalysis. This study demonstrates that loop motion during catalysis can be interrogated on the millisecond time scale.
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Affiliation(s)
- Mahesh Aitha
- Department of Chemistry and Biochemistry, Miami University, 650 East High Street, Oxford, Ohio 45056, USA
| | - Lindsay Moritz
- Department of Chemistry and Biochemistry, Miami University, 650 East High Street, Oxford, Ohio 45056, USA
| | - Indra D. Sahu
- Department of Chemistry and Biochemistry, Miami University, 650 East High Street, Oxford, Ohio 45056, USA
| | - Omar Sanyurah
- Department of Chemistry and Biochemistry, Miami University, 650 East High Street, Oxford, Ohio 45056, USA
| | - Zahilyn Roche
- Department of Chemistry and Biochemistry, Miami University, 650 East High Street, Oxford, Ohio 45056, USA
| | - Robert McCarrick
- Department of Chemistry and Biochemistry, Miami University, 650 East High Street, Oxford, Ohio 45056, USA
| | - Gary A. Lorigan
- Department of Chemistry and Biochemistry, Miami University, 650 East High Street, Oxford, Ohio 45056, USA
| | - Brian Bennett
- Physics Department, Marquette University, 540 N. 15th Street, Milwaukee, Wisconsin 53233, USA, and Department of Biophysics, Medical College of Wisconsin, 8701 W. Watertown Plank Road, Milwaukee, Wisconsin 53226, USA
| | - Michael W. Crowder
- Department of Chemistry and Biochemistry, Miami University, 650 East High Street, Oxford, Ohio 45056, USA
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21
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Mullineaux CW, Nürnberg DJ. Tracing the path of a prokaryotic paracrine signal. Mol Microbiol 2014; 94:1208-12. [DOI: 10.1111/mmi.12851] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/29/2014] [Indexed: 01/08/2023]
Affiliation(s)
- Conrad W. Mullineaux
- School of Biological and Chemical SciencesQueen Mary University of London Mile End Road London E1 4NS UK
- Freiburg Institute for Advanced Studies (FRIAS)University of Freiburg Freiburg Germany
| | - Dennis J. Nürnberg
- School of Biological and Chemical SciencesQueen Mary University of London Mile End Road London E1 4NS UK
- Department of Life SciencesImperial College London London SW7 2AZ UK
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22
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The trpE gene negatively regulates differentiation of heterocysts at the level of induction in Anabaena sp. strain PCC 7120. J Bacteriol 2014; 197:362-70. [PMID: 25384479 DOI: 10.1128/jb.02145-14] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Levels of 2-oxoglutarate (2-OG) reflect nitrogen status in many bacteria. In heterocystous cyanobacteria, a spike in the 2-OG level occurs shortly after the removal of combined nitrogen from cultures and is an integral part of the induction of heterocyst differentiation. In this work, deletion of one of the two annotated trpE genes in Anabaena sp. strain PCC 7120 resulted in a spike in the 2-OG level and subsequent differentiation of a wild-type pattern of heterocysts when filaments of the mutant were transferred from growth on ammonia to growth on nitrate. In contrast, 2-OG levels were unaffected in the wild type, which did not differentiate under the same conditions. An inverted-repeat sequence located upstream of trpE bound a central regulator of differentiation, HetR, in vitro and was necessary for HetR-dependent transcription of a reporter fusion and complementation of the mutant phenotype in vivo. Functional complementation of the mutant phenotype with the addition of tryptophan suggested that levels of tryptophan, rather than the demonstrated anthranilate synthase activity of TrpE, mediated the developmental response of the wild type to nitrate. A model is presented for the observed increase in 2-OG in the trpE mutant.
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23
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Rivers OS, Videau P, Callahan SM. Mutation of
sepJ
reduces the intercellular signal range of a
hetN
‐dependent paracrine signal, but not of a
patS
‐dependent signal, in the filamentous cyanobacterium
A
nabaena
sp. strain
PCC
7120. Mol Microbiol 2014; 94:1260-71. [DOI: 10.1111/mmi.12836] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/20/2014] [Indexed: 02/06/2023]
Affiliation(s)
- Orion S. Rivers
- Department of MicrobiologyUniversity of Hawai'i at Mānoa Honolulu HI 96822 USA
| | - Patrick Videau
- Department of MicrobiologyUniversity of Hawai'i at Mānoa Honolulu HI 96822 USA
| | - Sean M. Callahan
- Department of MicrobiologyUniversity of Hawai'i at Mānoa Honolulu HI 96822 USA
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24
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Sahu ID, Kroncke BM, Zhang R, Dunagan MM, Smith HJ, Craig A, McCarrick RM, Sanders CR, Lorigan GA. Structural investigation of the transmembrane domain of KCNE1 in proteoliposomes. Biochemistry 2014; 53:6392-401. [PMID: 25234231 PMCID: PMC4196734 DOI: 10.1021/bi500943p] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
![]()
KCNE1 is a single-transmembrane protein
of the KCNE family that modulates the function of voltage-gated potassium
channels, including KCNQ1. Hereditary mutations in KCNE1 have been
linked to diseases such as long QT syndrome (LQTS), atrial fibrillation,
sudden infant death syndrome, and deafness. The transmembrane domain
(TMD) of KCNE1 plays a key role in mediating the physical association
with KCNQ1 and in subsequent modulation of channel gating kinetics
and conductance. However, the mechanisms associated with these roles
for the TMD remain poorly understood, highlighting a need for experimental
structural studies. A previous solution NMR study of KCNE1 in LMPG
micelles revealed a curved transmembrane domain, a structural feature
proposed to be critical to KCNE1 function. However, this curvature
potentially reflects an artifact of working in detergent micelles.
Double electron electron resonance (DEER) measurements were conducted
on KCNE1 in LMPG micelles, POPC/POPG proteoliposomes, and POPC/POPG
lipodisq nanoparticles to directly compare the structure of the TMD
in a variety of different membrane environments. Experimentally derived
DEER distances coupled with simulated annealing molecular dynamic
simulations were used to probe the bilayer structure of the TMD of
KCNE1. The results indicate that the structure is helical in proteoliposomes
and is slightly curved, which is consistent with the previously determined
solution NMR structure in micelles. The evident resilience of the
curvature in the KCNE1 TMD leads us to hypothesize that the curvature
is likely to be maintained upon binding of the protein to the KCNQ1
channel.
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Affiliation(s)
- Indra D Sahu
- Department of Chemistry and Biochemistry, Miami University , Oxford, Ohio 45056, United States
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25
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Flaherty BL, Johnson DBF, Golden JW. Deep sequencing of HetR-bound DNA reveals novel HetR targets in Anabaena sp. strain PCC7120. BMC Microbiol 2014; 14:255. [PMID: 25278209 PMCID: PMC4192349 DOI: 10.1186/s12866-014-0255-x] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2013] [Accepted: 09/25/2014] [Indexed: 11/25/2022] Open
Abstract
Background Anabaena (also Nostoc) sp. strain PCC7120, hereafter Anabaena, is a cyanobacterium that fixes atmospheric N2 in specialized cells called heterocysts. Heterocyst differentiation is regulated by a homodimeric transcription factor, HetR. HetR is expressed at a basal level in all cells but its expression increases in differentiating cells early after nitrogen deprivation. HetR is required for heterocyst development, and therefore nitrogen fixation and diazotrophic growth. Overexpression of HetR leads to multiple contiguous heterocysts (Mch phenotype). HetR binds in vitro to DNA fragments upstream of several genes upregulated in heterocysts, including hetZ, hetP, hepA, patS, pknE, and hetR itself. HetR binds an inverted repeat sequence upstream of a few of these genes; however, HetR binds to promoters that do not contain this sequence, such as the promoter regions for patS and pknE. Results We employed chromatin pull-down and deep sequencing (ChIP-seq) to globally identify HetR DNA targets in vivo at six hours after fixed-nitrogen deprivation. We identified novel DNA binding targets of tagged HetR-6xHis and defined a consensus HetR binding site from these HetR target sequences. Promoter-gfp reporter fusions were used to determine the spatiotemporal expression of four potential HetR-target genes. The promoter region for asr1469 was expressed transiently in differentiating heterocysts, alr3758 was upregulated in heterocysts, asl2028 was expressed in vegetative cells, and alr2242 was derepressed in vegetative cells of a hetR mutant strain. Conclusions In addition to identifying known HetR target genes hetR and hetP, the ChIP-seq data were used to identify new potential HetR targets and to define a consensus HetR-binding site. The in vivo ChIP-seq analysis of HetR’s regulon suggests a possible role for HetR in vegetative cells in addition to its role in heterocyst development. The potential HetR target genes identified in this study provide new subjects for future work on the role of HetR in gene regulation. Electronic supplementary material The online version of this article (doi:10.1186/s12866-014-0255-x) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Britt L Flaherty
- Division of Biological Sciences, University of California San Diego, La Jolla, CA, USA. .,Present address: Illumina, Inc., San Diego, CA, USA.
| | - David B F Johnson
- Division of Biological Sciences, University of California San Diego, La Jolla, CA, USA. .,Present address: Peterson, Wilmarth, and Robertson, LLP, Washington, DC, USA.
| | - James W Golden
- Division of Biological Sciences, University of California San Diego, La Jolla, CA, USA.
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26
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Aitha M, Richmond TK, Hu Z, Hetrick A, Reese R, Gunther A, McCarrick R, Bennett B, Crowder MW. Dilution of dipolar interactions in a spin-labeled, multimeric metalloenzyme for DEER studies. J Inorg Biochem 2014; 136:40-6. [PMID: 24742748 PMCID: PMC4733626 DOI: 10.1016/j.jinorgbio.2014.03.010] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2013] [Revised: 03/17/2014] [Accepted: 03/18/2014] [Indexed: 01/28/2023]
Abstract
The metallo-β-lactamases (MβLs), which require one or two Zn(II) ions in their active sites for activity, hydrolyze the amide bond in β-lactam-containing antibiotics, and render the antibiotics inactive. All known MβLs contain a mobile element near their active sites, and these mobile elements have been implicated in the catalytic mechanisms of these enzymes. However little is known about the dynamics of these elements. In this study, we prepared a site-specific, double spin-labeled analog of homotetrameric MβL L1 with spin labels at positions 163 and 286 and analyzed the sample with DEER (double electron electron resonance) spectroscopy. Four unique distances were observed in the DEER distance distribution, and these distances were assigned to the desired intramolecular dipolar coupling (between spin labels at positions 163 and 286 in one subunit) and to intermolecular dipolar couplings. To rid the spin-labeled analog of L1 of the intermolecular couplings, spin-labeled L1 was "diluted" by unfolding/refolding the spin-labeled enzyme in the presence of excess wild-type L1. DEER spectra of the resulting, spin-diluted enzyme revealed a single distance corresponding to the desire intramolecular dipolar coupling.
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Affiliation(s)
- Mahesh Aitha
- Department of Chemistry and Biochemistry, Miami University, 160 Hughes Hall, Oxford, OH 45056, United States
| | - Timothy K Richmond
- Department of Chemistry and Biochemistry, Miami University, 160 Hughes Hall, Oxford, OH 45056, United States
| | - Zhenxin Hu
- Department of Chemistry and Biochemistry, Miami University, 160 Hughes Hall, Oxford, OH 45056, United States
| | - Alyssa Hetrick
- Department of Chemistry and Biochemistry, Miami University, 160 Hughes Hall, Oxford, OH 45056, United States
| | - Raquel Reese
- Department of Chemistry and Biochemistry, Miami University, 160 Hughes Hall, Oxford, OH 45056, United States
| | - Althea Gunther
- Department of Chemistry and Biochemistry, Miami University, 160 Hughes Hall, Oxford, OH 45056, United States
| | - Robert McCarrick
- Department of Chemistry and Biochemistry, Miami University, 160 Hughes Hall, Oxford, OH 45056, United States
| | - Brian Bennett
- Department of Biophysics, National Biomedical EPR Center, Medical College of Wisconsin, Milwaukee, WI 53226, United States
| | - Michael W Crowder
- Department of Chemistry and Biochemistry, Miami University, 160 Hughes Hall, Oxford, OH 45056, United States.
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27
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Abstract
In response to a lack of environmental combined nitrogen, the filamentous cyanobacterium Anabaena sp. strain PCC 7120 differentiates nitrogen-fixing heterocyst cells in a periodic pattern. HetR is a transcription factor that coordinates the regulation of this developmental program. An inverted repeat-containing sequence in the hepA promoter required for proheterocyst-specific transcription was identified based on sequence similarity to a previously characterized binding site for HetR in the promoter of hetP. The binding affinity of HetR for the hepA site is roughly an order of magnitude lower than that for the hetP binding site. A BLAST search of the Anabaena genome identified 166 hepA-like sites that occur as single or tandem sites (two binding sites separated by 13 bp). The vast majority of these sites are present in predicted intergenic regions. HetR bound five representative single binding sites in vitro, and binding was abrogated by transversions in the binding sites that conserved the inverted repeat nature of the sites. Binding to four representative tandem sites was not observed. Transcriptional fusions of the green fluorescent protein gene gfp with putative promoter regions associated with the representative binding sites indicated that HetR could function as either an activator or repressor and that activation was cell-type specific. Taken together, we have expanded the direct HetR regulon and propose a model in which three categories of HetR binding sites, based on binding affinity and nucleotide sequence, contribute to three of the four phases of differentiation.
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Sahu ID, McCarrick RM, Troxel KR, Zhang R, Smith HJ, Dunagan MM, Swartz MS, Rajan PV, Kroncke BM, Sanders CR, Lorigan GA. DEER EPR measurements for membrane protein structures via bifunctional spin labels and lipodisq nanoparticles. Biochemistry 2013; 52:6627-32. [PMID: 23984855 DOI: 10.1021/bi4009984] [Citation(s) in RCA: 91] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Pulsed EPR DEER structural studies of membrane proteins in a lipid bilayer have often been hindered by difficulties in extracting accurate distances when compared to those of globular proteins. In this study, we employed a combination of three recently developed methodologies, (1) bifunctional spin labels (BSL), (2) SMA-Lipodisq nanoparticles, and (3) Q band pulsed EPR measurements, to obtain improved signal sensitivity, increased transverse relaxation time, and more accurate and precise distances in DEER measurements on the integral membrane protein KCNE1. The KCNE1 EPR data indicated an ∼2-fold increase in the transverse relaxation time for the SMA-Lipodisq nanoparticles when compared to those of proteoliposomes and narrower distance distributions for the BSL when compared to those of the standard MTSL. The certainty of information content in DEER data obtained for KCNE1 in SMA-Lipodisq nanoparticles is comparable to that in micelles. The combination of techniques will enable researchers to potentially obtain more precise distances in cases where the traditional spin labels and membrane systems yield imprecise distance distributions.
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Affiliation(s)
- Indra D Sahu
- Department of Chemistry and Biochemistry, Miami University , Oxford, Ohio 45056, United States
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Sahu ID, McCarrick RM, Lorigan GA. Use of electron paramagnetic resonance to solve biochemical problems. Biochemistry 2013; 52:5967-84. [PMID: 23961941 PMCID: PMC3839053 DOI: 10.1021/bi400834a] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Electron paramagnetic resonance (EPR) spectroscopy is a very powerful biophysical tool that can provide valuable structural and dynamic information about a wide variety of biological systems. The intent of this review is to provide a general overview for biochemists and biological researchers of the most commonly used EPR methods and how these techniques can be used to answer important biological questions. The topics discussed could easily fill one or more textbooks; thus, we present a brief background on several important biological EPR techniques and an overview of several interesting studies that have successfully used EPR to solve pertinent biological problems. The review consists of the following sections: an introduction to EPR techniques, spin-labeling methods, and studies of naturally occurring organic radicals and EPR active transition metal systems that are presented as a series of case studies in which EPR spectroscopy has been used to greatly further our understanding of several important biological systems.
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Affiliation(s)
- Indra D. Sahu
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH
| | | | - Gary A. Lorigan
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH
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Exploring the size limit of protein diffusion through the periplasm in cyanobacterium Anabaena sp. PCC 7120 using the 13 kDa iLOV fluorescent protein. Res Microbiol 2013; 164:710-7. [DOI: 10.1016/j.resmic.2013.05.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2013] [Accepted: 05/24/2013] [Indexed: 01/16/2023]
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Corrales-Guerrero L, Mariscal V, Flores E, Herrero A. Functional dissection and evidence for intercellular transfer of the heterocyst-differentiation PatS morphogen. Mol Microbiol 2013; 88:1093-105. [DOI: 10.1111/mmi.12244] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/22/2013] [Indexed: 11/29/2022]
Affiliation(s)
- Laura Corrales-Guerrero
- Instituto de Bioquímica Vegetal y Fotosíntesis; Consejo Superior de Investigaciones Científicas and Universidad de Sevilla; Américo Vespucio 49; E-41092; Seville; Spain
| | - Vicente Mariscal
- Instituto de Bioquímica Vegetal y Fotosíntesis; Consejo Superior de Investigaciones Científicas and Universidad de Sevilla; Américo Vespucio 49; E-41092; Seville; Spain
| | - Enrique Flores
- Instituto de Bioquímica Vegetal y Fotosíntesis; Consejo Superior de Investigaciones Científicas and Universidad de Sevilla; Américo Vespucio 49; E-41092; Seville; Spain
| | - Antonia Herrero
- Instituto de Bioquímica Vegetal y Fotosíntesis; Consejo Superior de Investigaciones Científicas and Universidad de Sevilla; Américo Vespucio 49; E-41092; Seville; Spain
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Structures of complexes comprised of Fischerella transcription factor HetR with Anabaena DNA targets. Proc Natl Acad Sci U S A 2013; 110:E1716-23. [PMID: 23610410 DOI: 10.1073/pnas.1305971110] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
HetR is an essential regulator of heterocyst development in cyanobacteria. Many mutations in HetR render Anabaena incapable of nitrogen fixation. The protein binds to a DNA palindrome upstream of hetP and other genes. We have determined the crystal structures of HetR complexed with palindromic DNA targets, 21, 23, and 29 bp at 2.50-, 3.00-, and 3.25-Å resolution, respectively. The highest-resolution structure shows fine details of specific protein-DNA interactions. The lower-resolution structures with longer DNA duplexes have similar interaction patterns and show how the flap domains interact with DNA in a sequence nonspecific fashion. Fifteen of 15 protein-DNA contacts predicted on the basis of the structure were confirmed by single amino acid mutations that abolished binding in vitro and complementation in vivo. A striking feature of the structure is the association of glutamate 71 from each subunit of the HetR dimer with three successive cytosines in each arm of the palindromic target, a feature that is conserved among all known heterocyst-forming cyanobacteria sequenced to date.
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Muro-Pastor AM, Hess WR. Heterocyst differentiation: from single mutants to global approaches. Trends Microbiol 2012; 20:548-57. [DOI: 10.1016/j.tim.2012.07.005] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2012] [Revised: 07/08/2012] [Accepted: 07/12/2012] [Indexed: 02/05/2023]
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34
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Yang Z, Liu Y, Borbat P, Zweier JL, Freed JH, Hubbell WL. Pulsed ESR dipolar spectroscopy for distance measurements in immobilized spin labeled proteins in liquid solution. J Am Chem Soc 2012; 134:9950-2. [PMID: 22676043 PMCID: PMC3409244 DOI: 10.1021/ja303791p] [Citation(s) in RCA: 160] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Pulsed electron spin resonance (ESR) dipolar spectroscopy (PDS) in combination with site-directed spin labeling is unique in providing nanometer-range distances and distributions in biological systems. To date, most of the pulsed ESR techniques require frozen solutions at cryogenic temperatures to reduce the rapid electron spin relaxation rate and to prevent averaging of electron-electron dipolar interaction due to the rapid molecular tumbling. To enable measurements in liquid solution, we are exploring a triarylmethyl (TAM)-based spin label with a relatively long relaxation time where the protein is immobilized by attachment to a solid support. In this preliminary study, TAM radicals were attached via disulfide linkages to substituted cysteine residues at positions 65 and 80 or 65 and 76 in T4 lysozyme immobilized on Sepharose. Interspin distances determined using double quantum coherence (DQC) in solution are close to those expected from models, and the narrow distance distribution in each case indicates that the TAM-based spin label is relatively localized.
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Affiliation(s)
- Zhongyu Yang
- Jules Stein Eye Institute and Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, USA
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35
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Du Y, Cai Y, Hou S, Xu X. Identification of the HetR recognition sequence upstream of hetZ in Anabaena sp. strain PCC 7120. J Bacteriol 2012; 194:2297-306. [PMID: 22389489 PMCID: PMC3347059 DOI: 10.1128/jb.00119-12] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2012] [Accepted: 02/23/2012] [Indexed: 11/20/2022] Open
Abstract
HetR is the master regulator of heterocyst differentiation in Anabaena sp. strain PCC 7120 and has been found to specifically bind to an inverted-repeat-containing region upstream of hetP, a heterocyst differentiation gene. However, no such inverted-repeat sequence can be found in promoters of other genes in the genome. hetZ is a gene involved in early heterocyst differentiation. As shown with the gfp reporter gene, transcription from P(hetZ) was correlated to the expression level of hetR and inhibition by RGSGR, the pentapeptide derived from the C terminus of PatS. As detected by electrophoretic mobility shift assay, a recombinant HetR showed specific binding to the region upstream of hetZ, and the binding was inhibited by RGSGR. Tests of a series of the upstream fragments delimited the HetR-binding site to a 40-bp region that shows similarity to that upstream of hetP. The introduction of substitutions of bases conserved in the two HetR-binding sites showed that at least 12 bases are required for recognition by HetR. Deletion of a 51-bp region containing the HetR-binding site completely eliminated the transcription activity of P(hetZ). Based on the HetR recognition sequence of hetZ, those upstream of hetR and patA are proposed.
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Affiliation(s)
- Ye Du
- The State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei, China
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Feldmann EA, Ni S, Sahu ID, Mishler CH, Levengood JD, Kushnir Y, McCarrick RM, Lorigan GA, Tolbert BS, Callahan SM, Kennedy MA. Differential Binding between PatS C-Terminal Peptide Fragments and HetR from Anabaena sp. PCC 7120. Biochemistry 2012; 51:2436-42. [DOI: 10.1021/bi300228n] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- Erik A. Feldmann
- Department of Chemistry and
Biochemistry, Miami University, Oxford,
Ohio 45056, United States
| | - Shuisong Ni
- Department of Chemistry and
Biochemistry, Miami University, Oxford,
Ohio 45056, United States
| | - Indra D. Sahu
- Department of Chemistry and
Biochemistry, Miami University, Oxford,
Ohio 45056, United States
| | - Clay H. Mishler
- Department of Chemistry and
Biochemistry, Miami University, Oxford,
Ohio 45056, United States
| | - Jeffrey D. Levengood
- Department of Chemistry and
Biochemistry, Miami University, Oxford,
Ohio 45056, United States
| | - Yegor Kushnir
- Department of Chemistry and
Biochemistry, Miami University, Oxford,
Ohio 45056, United States
| | - Robert M. McCarrick
- Department of Chemistry and
Biochemistry, Miami University, Oxford,
Ohio 45056, United States
| | - Gary A. Lorigan
- Department of Chemistry and
Biochemistry, Miami University, Oxford,
Ohio 45056, United States
| | - Blanton S. Tolbert
- Department of Chemistry and
Biochemistry, Miami University, Oxford,
Ohio 45056, United States
| | - Sean M. Callahan
- Department of Microbiology, University of Hawaii, Honolulu, Hawaii 96822, United
States
| | - Michael A. Kennedy
- Department of Chemistry and
Biochemistry, Miami University, Oxford,
Ohio 45056, United States
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37
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Higa KC, Rajagopalan R, Risser DD, Rivers OS, Tom SK, Videau P, Callahan SM. The RGSGR amino acid motif of the intercellular signalling protein, HetN, is required for patterning of heterocysts in Anabaena sp. strain PCC 7120. Mol Microbiol 2012; 83:682-93. [DOI: 10.1111/j.1365-2958.2011.07949.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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