Abstract:H-NS proteins act as osmotic sensors translating changes in osmolarity into altered DNA binding properties, thus, regulating enterobacterial genome organization and genes transcription. The molecular mechanism underlying the switching process and its conservation among H-NS family members remains elusive.Here, we focus on the H-NS family protein MvaT from P. aeruginosa and demonstrate experimentally that its protomer exists in two different conformations, corresponding to two different functional states. In th… Show more
“…The linker of H-NS was shown to be essential for the interdomain interaction between the N-terminal and C-terminal domain [64]. Studies on MvaT in our laboratory further support a model in which both an increase in ionic strength and the DNA substrate additively destabilize these interdomain interactions, inducing the dimers to release their second DNA-binding domain to bind and bridge a second DNA molecule in trans (figure 4 a ) [51]. Figure 4.H-NS-like protein DNA-binding modes and electrostatics.…”
Section: Protein–dna Complexes Formed By H-ns-like Proteinsmentioning
confidence: 83%
“…( a ) Schematic of the switching mechanism between H-NS-like proteins DNA-binding modes. The red/blue gradient represents the electrostatics of H-NS-like protein surfaces [51,61]. The red and blue are for negatively and positively charged surface regions, respectively.…”
Section: Protein–dna Complexes Formed By H-ns-like Proteinsmentioning
confidence: 99%
“…The interdomain interactions described above for H-NS and MvaT might be driven by the asymmetrical charge distribution within the protein sequence: the N-terminal domain is mainly negatively charged, while the linker and the DNA-binding motif are positively charged (figure 4 b , c ). Analysis of the average charge of the primary sequences of H-NS-like proteins revealed that this characteristic is a conserved feature among H-NS/MvaT proteins across species and extends to Lsr2 (figure 4 b – d ; electronic supplementary material) [51]. The conserved asymmetrical charge distribution might provide an explanation for how H-NS, MvaT and Lsr2 act as sensors of environmental changes.…”
Section: Protein–dna Complexes Formed By H-ns-like Proteinsmentioning
confidence: 99%
“…However, the stiffness of the MvaT–DNA filament is not affected by salt over the same concentration range [57]. The formation of DNA–DNA bridges by H-NS and MvaT is sensitive to both MgCl 2 and KCl [51,58,101]. Changes in MgCl 2 (0–10 mM) or KCl concentration (50–300 mM) drive a switch between the DNA stiffening mode and bridging mode.…”
Every organism across the tree of life compacts and organizes its genome with architectural chromatin proteins. While eukaryotes and archaea express histone proteins, the organization of bacterial chromosomes is dependent on nucleoid-associated proteins. In
Escherichia coli
and other proteobacteria, the histone-like nucleoid structuring protein (H-NS) acts as a global genome organizer and gene regulator. Functional analogues of H-NS have been found in other bacterial species: MvaT in
Pseudomonas
species, Lsr2 in actinomycetes and Rok in
Bacillus
species. These proteins complement
hns
−
phenotypes and have similar DNA-binding properties, despite their lack of sequence homology. In this review, we focus on the structural and functional characteristics of these four architectural proteins. They are able to bridge DNA duplexes, which is key to genome compaction, gene regulation and their response to changing conditions in the environment. Structurally the domain organization and charge distribution of these proteins are conserved, which we suggest is at the basis of their conserved environment responsive behaviour. These observations could be used to find and validate new members of this protein family and to predict their response to environmental changes.
“…The linker of H-NS was shown to be essential for the interdomain interaction between the N-terminal and C-terminal domain [64]. Studies on MvaT in our laboratory further support a model in which both an increase in ionic strength and the DNA substrate additively destabilize these interdomain interactions, inducing the dimers to release their second DNA-binding domain to bind and bridge a second DNA molecule in trans (figure 4 a ) [51]. Figure 4.H-NS-like protein DNA-binding modes and electrostatics.…”
Section: Protein–dna Complexes Formed By H-ns-like Proteinsmentioning
confidence: 83%
“…( a ) Schematic of the switching mechanism between H-NS-like proteins DNA-binding modes. The red/blue gradient represents the electrostatics of H-NS-like protein surfaces [51,61]. The red and blue are for negatively and positively charged surface regions, respectively.…”
Section: Protein–dna Complexes Formed By H-ns-like Proteinsmentioning
confidence: 99%
“…The interdomain interactions described above for H-NS and MvaT might be driven by the asymmetrical charge distribution within the protein sequence: the N-terminal domain is mainly negatively charged, while the linker and the DNA-binding motif are positively charged (figure 4 b , c ). Analysis of the average charge of the primary sequences of H-NS-like proteins revealed that this characteristic is a conserved feature among H-NS/MvaT proteins across species and extends to Lsr2 (figure 4 b – d ; electronic supplementary material) [51]. The conserved asymmetrical charge distribution might provide an explanation for how H-NS, MvaT and Lsr2 act as sensors of environmental changes.…”
Section: Protein–dna Complexes Formed By H-ns-like Proteinsmentioning
confidence: 99%
“…However, the stiffness of the MvaT–DNA filament is not affected by salt over the same concentration range [57]. The formation of DNA–DNA bridges by H-NS and MvaT is sensitive to both MgCl 2 and KCl [51,58,101]. Changes in MgCl 2 (0–10 mM) or KCl concentration (50–300 mM) drive a switch between the DNA stiffening mode and bridging mode.…”
Every organism across the tree of life compacts and organizes its genome with architectural chromatin proteins. While eukaryotes and archaea express histone proteins, the organization of bacterial chromosomes is dependent on nucleoid-associated proteins. In
Escherichia coli
and other proteobacteria, the histone-like nucleoid structuring protein (H-NS) acts as a global genome organizer and gene regulator. Functional analogues of H-NS have been found in other bacterial species: MvaT in
Pseudomonas
species, Lsr2 in actinomycetes and Rok in
Bacillus
species. These proteins complement
hns
−
phenotypes and have similar DNA-binding properties, despite their lack of sequence homology. In this review, we focus on the structural and functional characteristics of these four architectural proteins. They are able to bridge DNA duplexes, which is key to genome compaction, gene regulation and their response to changing conditions in the environment. Structurally the domain organization and charge distribution of these proteins are conserved, which we suggest is at the basis of their conserved environment responsive behaviour. These observations could be used to find and validate new members of this protein family and to predict their response to environmental changes.
“…In order to investigate whether Gbn alters DNA conformation in vitro , we performed Tethered Particle Motion (TPM) experiments (68). If the binding of a protein to DNA induces bends or affects DNA stiffness this translates into a reduction or an increase of the root mean square displacement (RMS) respectively compared to that of bare DNA (69–71). Here we used a 685 bp DNA substrate containing the gbn promoter region with 10 GATC(WT) sites.…”
Bacterial chromosome structure is organized by a diverse group of proteins collectively called nucleoid-associated proteins (NAPs). Many NAPs have been studied in detail in Streptomyces, including Lsr2, HupA, HupS, and sIHF. Here, we show that SCO1839 represents a novel family of small NAPs unique to Actinobacteria and recognizes a consensus sequence consisting of GATC followed by (A/T)T. The protein was designated Gbn for GATC-binding NAP. Chromatin immunoprecipitation sequencing (ChIP-Seq) detected more than 2800 binding regions, encompassing some 3600 GATCWT motifs, which comprise 55% of all motifs in the S. coelicolor genome. DNA binding of Gbn in vitro increased DNA stiffness but not compaction, suggesting a role in regulation rather than chromosome organization. Despite the huge number of binding sites, the DNA binding profiles were nearly identical during vegetative and aerial growth. The exceptions were SCO1311 and SCOt32, for a tRNA editing enzyme and a tRNA that recognises the rare leucine codon CUA, respectively, which were nearly exclusively bound during vegetative growth. Deletion of gbn led to pleiotropic alterations in developmental timing, morphogenesis and antibiotic production. Taken together, our data show that Gbn is a highly pleiotropic NAP that impacts growth and development in streptomycetes.
The chromosomal DNA of bacteria is folded into a compact body called the nucleoid, which is composed essentially of DNA (≈80%), RNA (≈10%), and a number of different proteins (≈10%). These nucleoid proteins act as regulators of gene expression and influence the organization of the nucleoid by bridging, bending, or wrapping the DNA. These so-called architectural properties of nucleoid proteins are still poorly understood. For
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