Browse
Submit Data
Databases
API
Help

Dataset Information

0 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Single-molecule unzipping force analysis of HU-DNA complexes.

ABSTRACT: The genome of bacteria is organized and compacted by the action of nucleoid-associated proteins. These proteins are often present in tens of thousands of copies and bind with low specificity along the genome. DNA-bound proteins thus potentially act as roadblocks to the progression of machinery that moves along the DNA. In this study, we have investigated the effect of histone-like protein from strain U93 (HU), one of the key proteins involved in shaping the bacterial nucleoid, on DNA helix stability by mechanically unzipping single dsDNA molecules. Our study demonstrates that individually bound HU proteins have no observable effect on DNA helix stability, whereas HU proteins bound side-by-side within filaments increase DNA helix stability. As the stabilizing effect is small compared to the power of DNA-based motor enzymes, our results suggest that HU alone does not provide substantial hindrance to the motor's progression in vivo.

SUBMITTER: Dame RT

PROVIDER: S-EPMC3865359 | biostudies-literature | 2013 Oct

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

Single-molecule unzipping force analysis of HU-DNA complexes.

Dame Remus T RT Hall Michael A MA Wang Michelle D MD

Chembiochem : a European journal of chemical biology 20130902 15

The genome of bacteria is organized and compacted by the action of nucleoid-associated proteins. These proteins are often present in tens of thousands of copies and bind with low specificity along the genome. DNA-bound proteins thus potentially act as roadblocks to the progression of machinery that moves along the DNA. In this study, we have investigated the effect of histone-like protein from strain U93 (HU), one of the key proteins involved in shaping the bacterial nucleoid, on DNA helix stabi ...[more]

PMID: 24000171

Similar Datasets

Single-Molecule Force Spectroscopy Studies of APOBEC3A-Single-Stranded DNA Complexes.

Project description:APOBEC3A (A3A) inhibits the replication of a range of viruses and transposons and might also play a role in carcinogenesis. It is a single-domain deaminase enzyme that interacts with single-stranded DNA (ssDNA) and converts cytidines to uridines within specific trinucleotide contexts. Although there is abundant information that describes the potential biological activities of A3A, the interplay between binding ssDNA and sequence-specific deaminase activity remains controversial. Using a single-molecule atomic force microscopy spectroscopy approach developed by Shlyakhtenko et al. [(2015) Sci. Rep. 5, 15648], we determine the stability of A3A in complex with different ssDNA sequences. We found that the strength of the complex is sequence-dependent, with more stable complexes formed with deaminase-specific sequences. A correlation between the deaminase activity of A3A and the complex strength was identified. The ssDNA binding properties of A3A and those for A3G are also compared and discussed.

| S-EPMC4932870 | biostudies-literature

Pause point spectra in DNA constant-force unzipping.

Project description:Under constant applied force, the separation of double-stranded DNA into two single strands is known to proceed through a series of pauses and jumps. Given experimental traces of constant-force unzipping, we present a method whereby the locations of pause points can be extracted in the form of a pause point spectrum. A simple theoretical model of DNA constant-force unzipping is presented, which generates theoretical pause point spectra through Monte Carlo simulation of the unzipping process. The locations of peaks in the experimental and theoretical pause point spectra are found to be nearly coincident below 6000 basepairs for unzipping the bacteriophage lambda-genome. The model only requires the sequence, temperature, and a set of empirical basepair binding and stacking energy parameters, and the good agreement with experiment suggests that pause point locations are primarily determined by the DNA sequence. The model is also used to predict pause point spectra for the bacteriophage phi X174 genome. The algorithm for extracting the pause point spectrum might also be useful for studying related systems which exhibit pausing behavior such as molecular motors.

| S-EPMC1305371 | biostudies-literature

Single-molecule dynamics of the DNA-EcoRII protein complexes revealed with high-speed atomic force microscopy.

Project description:The study of interactions of protein with DNA is important for gaining a fundamental understanding of how numerous biological processes occur, including recombination, transcription, repair, etc. In this study, we use the EcoRII restriction enzyme, which employs a three-site binding mechanism to catalyze cleavage of a single recognition site. Using high-speed atomic force microscopy (HS-AFM) to image single-molecule interactions in real time, we were able to observe binding, translocation, and dissociation mechanisms of the EcoRII protein. The results show that the protein can translocate along DNA to search for the specific binding site. Also, once specifically bound at a single site, the protein is capable of translocating along the DNA to locate the second specific binding site. Furthermore, two alternative modes of dissociation of the EcoRII protein from the loop structure were observed, which result in the protein stably bound as monomers to two sites or bound to a single site as a dimer. From these observations, we propose a model in which this pathway is involved in the formation and dynamics of a catalytically active three-site complex.

| S-EPMC2784205 | biostudies-literature

Single molecule force spectroscopy on G-quadruplex DNA.

Project description: Not available

| S-EPMC2902544 | biostudies-literature

Probing DNA clamps with single-molecule force spectroscopy.

Project description:Detailed mechanisms of DNA clamps in prokaryotic and eukaryotic systems were investigated by probing their mechanics with single-molecule force spectroscopy. Specifically, the mechanical forces required for the Escherichia coli and Saccharomyces cerevisiae clamp opening were measured at the single-molecule level by optical tweezers. Steered molecular dynamics simulations further examined the forces involved in DNA clamp opening from the perspective of the interface binding energies associated with the clamp opening processes. In combination with additional molecular dynamics simulations, we identified the contact networks between the clamp subunits that contribute significantly to the interface stability of the S.cerevisiae and E. coli clamps. These studies provide a vivid picture of the mechanics and energy landscape of clamp opening and reveal how the prokaryotic and eukaryotic clamps function through different mechanisms.

| S-EPMC3763527 | biostudies-literature

DNA base pair resolution by single molecule force spectroscopy.

Project description:The forces that hold complementary strands of DNA together in a double helix, and the role of base mismatches in these, are examined by single molecule force spectroscopy using an atomic force microscope (AFM). These forces are important when considering the binding of proteins to DNA, since these proteins often mechanically stretch the DNA during their action. In AFM measurement of forces, there is an inherent instrumental limitation that makes it difficult to compare results from different experimental runs. This is circumvented by using an oligonucleotide microarray, which allowed a direct comparison of the forces between perfectly matched short oligonucleotides and those containing a single or double mismatch. Through this greatly increased sensitivity, the force contribution of a single AT base pair was derived. The results indicate that the contribution to forces from the stacking interactions is more important than that from hydrogen bonding.

| S-EPMC519116 | biostudies-literature

Biophysical characterization of DNA binding from single molecule force measurements.

Project description:Single molecule force spectroscopy is a powerful method that uses the mechanical properties of DNA to explore DNA interactions. Here we describe how DNA stretching experiments quantitatively characterize the DNA binding of small molecules and proteins. Small molecules exhibit diverse DNA binding modes, including binding into the major and minor grooves and intercalation between base pairs of double-stranded DNA (dsDNA). Histones bind and package dsDNA, while other nuclear proteins such as high mobility group proteins bind to the backbone and bend dsDNA. Single-stranded DNA (ssDNA) binding proteins slide along dsDNA to locate and stabilize ssDNA during replication. Other proteins exhibit binding to both dsDNA and ssDNA. Nucleic acid chaperone proteins can switch rapidly between dsDNA and ssDNA binding modes, while DNA polymerases bind both forms of DNA with high affinity at distinct binding sites at the replication fork. Single molecule force measurements quantitatively characterize these DNA binding mechanisms, elucidating small molecule interactions and protein function.

| S-EPMC2930095 | biostudies-literature

Single-molecule DNA unzipping reveals asymmetric modulation of a transcription factor by its binding site sequence and context.

Project description:Most functional transcription factor (TF) binding sites deviate from their 'consensus' recognition motif, although their sites and flanking sequences are often conserved across species. Here, we used single-molecule DNA unzipping with optical tweezers to study how Egr-1, a TF harboring three zinc fingers (ZF1, ZF2 and ZF3), is modulated by the sequence and context of its functional sites in the Lhb gene promoter. We find that both the core 9 bp bound to Egr-1 in each of the sites, and the base pairs flanking them, modulate the affinity and structure of the protein-DNA complex. The effect of the flanking sequences is asymmetric, with a stronger effect for the sequence flanking ZF3. Characterization of the dissociation time of Egr-1 revealed that a local, mechanical perturbation of the interactions of ZF3 destabilizes the complex more effectively than a perturbation of the ZF1 interactions. Our results reveal a novel role for ZF3 in the interaction of Egr-1 with other proteins and the DNA, providing insight on the regulation of Lhb and other genes by Egr-1. Moreover, our findings reveal the potential of small changes in DNA sequence to alter transcriptional regulation, and may shed light on the organization of regulatory elements at promoters.

| S-EPMC5815098 | biostudies-literature

Quantitative detection of small molecule/DNA complexes employing a force-based and label-free DNA-microarray.

Project description:Force-based ligand detection is a promising method to characterize molecular complexes label-free at physiological conditions. Because conventional implementations of this technique, e.g., based on atomic force microscopy or optical traps, are low-throughput and require extremely sensitive and sophisticated equipment, this approach has to date found only limited application. We present a low-cost, chip-based assay, which combines high-throughput force-based detection of dsDNA.ligand interactions with the ease of fluorescence detection. Within the comparative unbinding force assay, many duplicates of a target DNA duplex are probed against a defined reference DNA duplex each. The fractions of broken target and reference DNA duplexes are determined via fluorescence. With this assay, we investigated the DNA binding behavior of artificial pyrrole-imidazole polyamides. These small compounds can be programmed to target specific dsDNA sequences and distinguish between D- and L-DNA. We found that titration with polyamides specific for a binding motif, which is present in the target DNA duplex and not in the reference DNA duplex, reliably resulted in a shift toward larger fractions of broken reference bonds. From the concentration dependence nanomolar to picomolar dissociation constants of dsDNA.ligand complexes were determined, agreeing well with prior quantitative DNAase footprinting experiments. This finding corroborates that the forced unbinding of dsDNA in presence of a ligand is a nonequilibrium process that produces a snapshot of the equilibrium distribution between dsDNA and dsDNA.ligand complexes.

| S-EPMC2711479 | biostudies-literature

Resolving dual binding conformations of cellulosome cohesin-dockerin complexes using single-molecule force spectroscopy.

Project description:Receptor-ligand pairs are ordinarily thought to interact through a lock and key mechanism, where a unique molecular conformation is formed upon binding. Contrary to this paradigm, cellulosomal cohesin-dockerin (Coh-Doc) pairs are believed to interact through redundant dual binding modes consisting of two distinct conformations. Here, we combined site-directed mutagenesis and single-molecule force spectroscopy (SMFS) to study the unbinding of Coh:Doc complexes under force. We designed Doc mutations to knock out each binding mode, and compared their single-molecule unfolding patterns as they were dissociated from Coh using an atomic force microscope (AFM) cantilever. Although average bulk measurements were unable to resolve the differences in Doc binding modes due to the similarity of the interactions, with a single-molecule method we were able to discriminate the two modes based on distinct differences in their mechanical properties. We conclude that under native conditions wild-type Doc from Clostridium thermocellum exocellulase Cel48S populates both binding modes with similar probabilities. Given the vast number of Doc domains with predicted dual binding modes across multiple bacterial species, our approach opens up new possibilities for understanding assembly and catalytic properties of a broad range of multi-enzyme complexes.

| S-EPMC4728124 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

Tweets

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data