The RecX protein, a very active natural RecA protein inhibitor, can completely disassemble filaments at nanomolar concentrations that are two to three orders of magnitude lower than protein. Based on the structure complex with presynaptic filament, we designed short first in class α-helical peptide both inhibits activities vitro and blocks bacterial SOS-response vivo. was using SEQOPT, novel method for global sequence optimization α-helices. SEQOPT produces artificial sequences containing...

Abstract A large variety of short biologically active peptides possesses antioxidant, antibacterial, antitumour, anti-ageing and anti-inflammatory activity, involved in the regulation neuro-immuno-endocrine system functions, cell apoptosis, proliferation differentiation. Therefore, mechanisms their biological activity are attracting increasing attention not only modern molecular biology, biochemistry biophysics, but also pharmacology medicine. In this work, we systematically analysed ability...

RecA protein mediates homologous recombination repair in bacteria through assembly of long helical filaments on ssDNA an ATP-dependent manner. RecX, important negative regulator RecA, is known to inhibit activity by stimulating the disassembly nucleoprotein filaments. Here we use a single-molecule approach address regulation (Escherichia coli) RecA-ssDNA RecX (E. within framework distinct conformational states filament. Our findings revealed that effectively binds inactive conformation and...

Using molecular modeling techniques we have built the full atomic structure and performed dynamics simulations for complexes formed by Escherichia coli RecX protein with a single-stranded oligonucleotide RecA presynaptic filament. Based on SANS experimental data sandwich-like filament two chains of monomers bound to opposite sides single stranded DNA is proposed RecX::ssDNA complex. The model RecX::RecA::ssDNA include binding into grove RecA::ssDNA that occurs mainly via Coulomb interactions...

The wild-type Escherichia coli RecA protein is a recombinase platform with unrealized recombination potential. We have explored the factors affecting during conjugation quantitative assay. Regulatory proteins that affect function capacity to increase or decrease frequencies by up sixfold. Autoinhibition C-terminus can frequency fourfold. greatest changes in measured here are brought about point mutations recA gene. variants more than 50-fold. thus possesses an inherently broad functional...

The DprA protein has been implicated in the protection of incoming DNA. However, presence dprA gene family members, also known as smf, across diverse bacterial species suggests a broader functionality for their products. We examined role Escherichia coli DprA/Smf homologue conjugation. Remarkably, Bacillus subtilis dprA/smf can complement an E. mutant, indicating interchangeability genes between competent and non-competent conjugational processes. forms complex with DNA, facilitating...

The RecX protein of Escherichia coli inhibits the extension RecA filaments on DNA, presumably by binding to and blocking growing filament end. direct single-stranded DNA is weak, previous reports suggested that did not explain effects RecX. We now demonstrate elevated concentrations SSB greatly moderate protein. High yeast RPA have same effect, suggesting effect species-specific or even specific bacterial proteins. A SSB-RecX interaction thus unlikely. suggest access DNA. evident competition...

The replacement of Escherichia coli recA gene ( Ec ) with the Pseudomonas aeruginosa Pa in cells results constitutive hyper‐recombination (high frequency recombination exchanges per unit length DNA) absence SOS response. To understand biochemical basis this unusual vivo phenotype, we compared vitro properties RecA protein those protein. Consistent activity, appeared to be more proficient both joint molecule formation, producing extensive DNA networks strand exchange reaction, and competition...

ABSTRACT The radA gene predicted to be responsible for homologous recombination in a hyperthermophilic archaeon, Desulfurococcus amylolyticus , was cloned, sequenced, and overexpressed Escherichia coli cells. deduced amino acid sequence of the product, RadA, more similar human Rad51 protein (65% homology) than E. RecA (35%). A highly purified RadA shown exclusively catalyze single-stranded DNA-dependent ATP hydrolysis, which monitored presynaptic recombinational complex formation, at...

The filament structures of the self‐polymers RecA proteins from Escherichia coli and Pseudomonas aeruginosa , their complexes with ATPγS, phage M13 single‐stranded DNA (ssDNA) tertiary RecA::ATPγS::ssDNA were compared by small angle neutron scattering. A model was developed that allowed for an analytical solution scattering on a long helical filament, making it possible to obtain pitch mean diameter protein curves. results suggest structure filaments formed these two proteins, particularly...

The RecA recombinase of Escherichia coli has not evolved to optimally promote DNA pairing and strand exchange, the key processes recombinational repair. Instead, function protein represents an evolutionary compromise between necessary levels repair potentially deleterious consequences functionality. A variant, D112R, promotes conjugational recombination at substantially enhanced levels. However, expression D112R in E. results a reduction cell growth rates. This report documents substantial...

In Escherichia coli, a relatively low frequency of recombination exchanges (FRE) is predetermined by the activity RecA protein, as modulated complex regulatory program involving both autoregulation and other factors. The protein Pseudomonas aeruginosa (RecA(Pa)) exhibits more robust recombinase than its E. coli counterpart (RecA(Ec)). Low-level expression RecA(Pa) in cells results hyperrecombination (an increase FRE) even presence RecA(Ec). This genetic effect supported biochemical finding...

RecAX53 is a chimeric variant of the Escherichia coli RecA protein (RecAEc) that contains part central domain Pseudomonas aeruginosa (RecAPa), encompassing region differs from RecAEc at 12 amino acid positions. Like RecAPa, this chimera exhibits hyperrecombination activity in E. cells, increasing frequency recombination exchanges per DNA unit length (FRE). confers largest increase FRE observed to date. The contrasting properties and RecAPa are manifested by vivo differences dependence value...

Serratia proteamaculans synthesizes the intracellular metalloprotease protealysin. This work was aimed at searching for bacterial substrates of protealysin among proteins responsible replication and cell division. We have shown that unlimitedly cleaves SOS response protein RecA. Even 20% cleaved RecA in solution appears to be incorporated into polymer uncleaved monomers, preventing further polymerization inhibiting ATPase activity. Transformation Escherichia coli with a plasmid carrying gene...

The RecA protein plays a key role in bacterial homologous recombination (HR) and acts through assembly of long helical filaments around single-stranded DNA the presence ATP. Large-scale conformational changes induced by ATP hydrolysis result transitions between stretched compressed forms filament. Here, using single-molecule approach, we show that nucleoprotein can exist two distinct interconvertible states depending on ADP monomer-monomer interface. Binding promotes cooperative directly...

Deinococcus radiodurans (Dr) has one of the most robust DNA repair systems, which is capable withstanding extreme doses ionizing radiation and other sources damage. DrRecA, a central enzyme recombinational repair, essential for radioresistance. In presence ATP, DrRecA forms nucleoprotein filaments on DNA, similar to bacterial RecA eukaryotic strand exchange proteins. However, catalyzes in unique reverse pathway. Here, we study dynamics formed individual molecules duplex single-stranded...

Abstract The DprA protein has been implicated in the protecton of incoming DNA. However, presence dprA gene family members, also known as smf, across diverse bacterial species suggests a broader functonality for their products. We eaamined role Escherichia coli DprA/Smf homologue conjugaton. Remarkably, Bacillus subtilis dprA/smf can complement an E. mutant, indicatng interchangeability genes between competent and non-competent conjugatonal processes. forms complex with DNA, facilitatng...