Putative uncharacterized protein ORFJ in retron EC67 Antibody

What is the Putative uncharacterized protein ORFJ in retron EC67?

ORFJ is a protein encoded within the retron EC67 genetic element found in Escherichia coli. Retron EC67 is located at a position equivalent to 19 min on the E. coli K-12 chromosome and consists of a unique 34-kilobase sequence flanked by direct repeats of a 26-base-pair sequence . The ORFJ protein's function remains largely uncharacterized, though it is part of a retron system involved in bacterial anti-phage defense. Notably, within the 34-kilobase sequence, an open reading frame of 285 residues has been identified that displays 44% sequence identity with the E. coli Dam methylase , suggesting potential DNA methylation activity that may play a role in the retron's defense mechanism.

How does retron EC67 function in bacterial immunity?

Retron EC67 functions as part of bacterial immunity through a mechanism involving reverse transcription and effector proteins. The retron defense system is generally composed of:

• A reverse transcriptase (RT)

• Non-coding RNA (ncRNA) - msrmsd

• Accessory proteins with various enzymatic functions

The RT produces satellite msDNA molecules using msd RNA as a template . This process creates a branched DNA-RNA hybrid where the msd DNA and msr RNA are covalently joined via a 2'-5' phosphodiester bond . For retron EC67 specifically, it appears to be activated by phage-encoded proteins involved in DNA degradation, such as DenB from phage T2 and protein A1 from phages T5n and ΦSP15m . When the retron senses these phage proteins during infection, it triggers a defensive response that likely involves abortive infection to protect the bacterial population.

What are the structural components of retrons like EC67?

Retrons consist of three primary components that form a tripartite system:

In retron EC67, the system has been integrated into the bacterial genome as part of a 34-kilobase element . The region includes multiple open reading frames, including ORFJ, which may contribute to the defense function. The integration of retron EC67 into the E. coli genome appears to have occurred through a mechanism related to transposition or phage integration, as evidenced by the flanking direct repeats .

What are the validated applications for the ORFJ in retron EC67 antibody?

According to the product information provided by CUSABIO, the Putative uncharacterized protein ORFJ in retron EC67 antibody has been validated for the following applications :

• ELISA (Enzyme-Linked Immunosorbent Assay)

• Western Blot (WB)

The antibody is a polyclonal antibody raised in rabbits using recombinant Escherichia coli ORFJ protein as the immunogen . It is supplied in liquid form with 50% glycerol, 0.01M PBS (pH 7.4), and 0.03% Proclin 300 as a preservative . The antibody has been antigen-affinity purified to ensure specificity for the ORFJ protein.

How can the ORFJ antibody be used to study retron activation during phage infection?

Methodological approach for studying retron activation:

• Infection setup:

  • Culture E. coli strains containing retron EC67

  • Infect with phages known to trigger retron defense (e.g., T5n, ΦSP15m, T2)

  • Collect samples at different time points post-infection

• Protein extraction and analysis:

  • Prepare whole-cell lysates from infected and uninfected bacteria

  • Perform Western blot analysis using the ORFJ antibody

  • Compare ORFJ protein levels and potential post-translational modifications

• Co-immunoprecipitation:

  • Use the ORFJ antibody to pull down protein complexes

  • Identify interaction partners via mass spectrometry

  • Confirm interactions with phage proteins that trigger retron EC67 (e.g., DenB, protein A1)

• Immunofluorescence microscopy:

  • Fix infected cells at various time points

  • Use fluorescently labeled ORFJ antibody

  • Observe subcellular localization changes during infection

This methodological approach can reveal the timing of ORFJ expression, its interaction partners, and its subcellular localization during phage infection, providing insights into its role in bacterial defense.

What controls should be included when working with the ORFJ antibody?

When working with the ORFJ in retron EC67 antibody, the following controls should be included:

Including these controls is crucial for ensuring experimental rigor and validating results obtained with the ORFJ antibody, particularly given its targeting of a putative uncharacterized protein.

How can researchers investigate the functional relationship between ORFJ and phage anti-retron mechanisms?

To investigate the functional relationship between ORFJ and phage anti-retron mechanisms, researchers should employ a multi-faceted approach:

• Genetic screening of phage escape mutants:

  • Culture phages on bacteria expressing retron EC67

  • Isolate phages that successfully infect despite the retron defense

  • Sequence these "escaper" phages to identify potential anti-retron genes

  • Compare with known anti-retron systems like Rad (retron anti-defense) from phage ΦSP15

• Heterologous expression system:

  • Clone ORFJ into an expression vector

  • Express in a non-retron-containing E. coli strain

  • Challenge with various phages

  • Assess whether ORFJ alone confers any resistance

• Domain analysis and mutagenesis:

  • Perform in silico analysis of ORFJ to identify functional domains

  • Generate domain deletion or point mutation variants

  • Test these variants for altered defense capability

  • Identify critical residues for function

• Protein-protein interaction studies:

  • Perform pull-down assays with tagged ORFJ

  • Use mass spectrometry to identify bacterial and phage protein interactors

  • Validate interactions using co-immunoprecipitation with the ORFJ antibody

  • Create an interaction network to understand ORFJ's role

• Comparative analysis with other retron systems:

  • Compare ORFJ with accessory proteins from other retrons

  • Identify conserved motifs or functional domains

  • Test cross-complementation between different retron systems

This approach would help determine whether ORFJ functions similarly to other retron accessory proteins and how phages might evade or counteract its activity.

What insights can be gained by studying ORFJ's potential role in DNA methylation?

Given that ORFJ shows 44% sequence identity with E. coli Dam methylase , investigating its potential DNA methylation activity could provide significant insights:

• Methylation activity assays:

  • Express and purify recombinant ORFJ protein

  • Perform in vitro methylation assays using radiolabeled S-adenosylmethionine

  • Test various DNA substrates, particularly those containing GATC sequences (Dam target)

  • Analyze methylation patterns using restriction enzyme digestion (DpnI/DpnII)

• Methylome analysis:

  • Compare DNA methylation patterns in strains with and without ORFJ expression

  • Use bisulfite sequencing or SMRT sequencing to map methylation sites genome-wide

  • Identify specific sequence motifs targeted by ORFJ

• Impact on phage infection:

  • Determine if ORFJ-mediated methylation affects phage DNA replication

  • Compare infection dynamics in strains expressing wild-type versus catalytically inactive ORFJ

  • Assess if methylation serves as a marker for phage DNA degradation

• Connection to retron defense mechanism:

  • Investigate if ORFJ methylation marks host DNA to protect it during defense

  • Test if methylation plays a role in distinguishing self from non-self DNA

  • Examine if methylation patterns change during phage infection

Of particular interest is the observation that there are three GATC sequences in the promoter region of the gene for reverse transcriptase in retron EC67 , suggesting potential autoregulation through methylation activity. This could reveal a sophisticated regulatory mechanism for retron activity.

How does ORFJ compare structurally and functionally to other retron accessory proteins?

A comprehensive comparison of ORFJ with other retron accessory proteins would involve:

Recent research has classified retrons into 13 different types based on their genetic structure and accessory proteins . Each type has distinct effector mechanisms. For example, retron Ec78 (Retron-Eco7) uses effector proteins PtuA and PtuB to degrade bacterial tRNA^Tyr , while retron Ec67 may employ a different mechanism, potentially involving DNA methylation through ORFJ. Understanding these differences would provide valuable insights into the diverse defense strategies employed by retrons.

What are the optimal conditions for using the ORFJ antibody in Western blot applications?

For optimal Western blot results with the ORFJ antibody, consider the following protocol:

• Sample preparation:

  • Harvest E. coli cells in log phase

  • Lyse cells using a buffer containing 50 mM Tris-HCl (pH 8.0), 150 mM NaCl, 1% Triton X-100, and protease inhibitors

  • Sonicate briefly to shear DNA

  • Centrifuge at 12,000 × g for 15 minutes at 4°C

  • Collect supernatant and determine protein concentration

• Gel electrophoresis and transfer:

  • Load 20-40 μg of protein per lane on a 12% SDS-PAGE gel

  • Run at 120V until adequate separation

  • Transfer to PVDF membrane (0.45 μm) at 100V for 1 hour or 30V overnight

• Immunoblotting:

  • Block membrane with 5% non-fat dry milk in TBST for 1 hour at room temperature

  • Incubate with ORFJ antibody at 1:1000 dilution in 5% BSA in TBST overnight at 4°C

  • Wash 3 times with TBST for 5 minutes each

  • Incubate with HRP-conjugated anti-rabbit secondary antibody at 1:5000 dilution for 1 hour

  • Wash 3 times with TBST for 5 minutes each

  • Develop using enhanced chemiluminescence

• Expected results:

  • ORFJ protein should appear at approximately 32-35 kDa (based on a 285 residue protein )

  • Positive control: extract from E. coli strain containing retron EC67

  • Negative control: extract from E. coli K-12 lacking retron EC67

Optimization may be required for specific experimental conditions, including adjusting antibody dilution, incubation time, or blocking reagent.

How can researchers efficiently isolate and study retron EC67 msDNA production?

To isolate and study msDNA produced by retron EC67, researchers should follow this methodological approach:

• msDNA isolation protocol:

  • Grow E. coli containing retron EC67 to mid-log phase

  • Harvest cells and resuspend in 10 mM Tris (pH 8.0), 1 mM EDTA

  • Add equal volume of phenol:chloroform (1:1)

  • Vortex vigorously and centrifuge at 12,000 × g for 10 minutes

  • Collect the aqueous phase and add 0.1 volume of 3M sodium acetate (pH 5.2)

  • Add 2.5 volumes of ethanol and incubate at -20°C for 30 minutes

  • Centrifuge at 12,000 × g for 15 minutes at 4°C

  • Wash pellet with 70% ethanol and resuspend in TE buffer

• Analysis methods:

  • Visualize msDNA using TBE/Urea gel electrophoresis

  • Confirm identity using Southern blot with probes specific to retron EC67 sequence

  • Quantify production using qPCR with primers specific to msDNA

  • Sequence msDNA using adapted unbiased sequencing approaches

• Factors affecting msDNA production:

  • Expression level of reverse transcriptase

  • Secondary structure of the msrmsd non-coding RNA

  • Growth phase and environmental conditions

  • Presence of phage infection or stress

• Comparative analysis:

  • Compare msDNA production between wild-type and ORFJ mutant strains

  • Assess whether ORFJ affects msDNA production or stability

  • Determine if msDNA production changes during phage infection

This approach allows for detailed characterization of msDNA production by retron EC67 and can reveal the potential role of ORFJ in this process.

What techniques can be used to determine if ORFJ functions in conjunction with the retron reverse transcriptase?

To investigate the functional relationship between ORFJ and the retron EC67 reverse transcriptase (RT), researchers should employ the following techniques:

• Co-expression and co-purification studies:

  • Create constructs expressing tagged versions of both proteins

  • Perform pull-down experiments to detect physical interaction

  • Use the ORFJ antibody for co-immunoprecipitation of RT

  • Analyze complexes using mass spectrometry

• Genetic deletion and complementation:

  • Generate deletion mutants of ORFJ and RT individually

  • Assess phenotypic effects on bacterial growth and phage resistance

  • Complement with plasmid-expressed wild-type or mutant versions

  • Test if defects in one component can be suppressed by overexpression of the other

• Functional assays:

  • In vitro reverse transcription assays with purified components

  • Compare RT activity with and without ORFJ protein

  • Test if ORFJ affects template selection, processivity, or fidelity of RT

  • Assess whether ORFJ influences the stability of the RT-msDNA complex

• Microscopy and localization:

  • Create fluorescently tagged versions of ORFJ and RT

  • Use fluorescence microscopy to determine subcellular localization

  • Perform FRET (Förster Resonance Energy Transfer) to detect close interaction

  • Track localization changes during phage infection

• Bioinformatic analysis:

  • Compare conservation patterns between ORFJ and RT across different bacterial strains

  • Assess co-evolution using methods like mutual information analysis

  • Predict interaction interfaces using protein modeling

Similar to the Rad protein from phage ΦSP15, which interacts with retron components to degrade ncRNA and prevent further synthesis of retron , ORFJ may have evolved to regulate RT activity or contribute to the defense mechanism in other ways.

How can researchers leverage retron EC67 and ORFJ for biotechnological applications?

Retrons have emerging applications in biotechnology, particularly in genome editing. Researchers can leverage retron EC67 and ORFJ in the following ways:

• Genome editing tools:

  • Engineer retron EC67 to produce single-stranded DNA templates for precise genome editing

  • Optimize ORFJ's potential role in enhancing msDNA production or stability

  • Develop a retron-based editing system with improved efficiency compared to existing systems

  • Create "multitrons" that can edit multiple genomic sites simultaneously

• DNA production systems:

  • Design retron EC67-based vectors for in vivo DNA production

  • Modify the msrmsd non-coding RNA to encode desired DNA sequences

  • Use ORFJ to potentially regulate or enhance DNA production

  • Develop high-throughput screening systems to identify optimal retron variants

• Anti-phage defense engineering:

  • Transfer retron EC67 defense systems to industrial bacterial strains

  • Engineer ORFJ to recognize specific phage proteins

  • Create synthetic defense systems combining retron EC67 components with other defense mechanisms

  • Develop phage-resistant bacterial strains for biotechnology applications

• Protein-binding DNA generation:

  • Engineer retron EC67 to produce "pretroDNA" with protein-binding sequences

  • Use for controlling protein subcellular localization

  • Create dynamic, controllable DNA-protein interaction networks

  • Develop new tools for synthetic biology applications

• DNA-free gene editing:

  • Develop all-RNA delivery strategies using retron EC67 components

  • Enable precise gene editing without introducing foreign DNA

  • Apply in therapeutic contexts where DNA integration is undesirable

Recent studies have demonstrated the versatility of retrons for precise genome editing across kingdoms of life , suggesting that retron EC67 and ORFJ could be valuable components for developing novel biotechnological tools.

What are the challenges in studying proteins like ORFJ in bacterial defense systems?

Studying putative uncharacterized proteins like ORFJ in bacterial defense systems presents several methodological challenges:

To overcome these challenges, researchers should employ a combination of genetic, biochemical, and computational approaches while considering the biological context in which ORFJ functions. Collaboration between experts in bacteriophage biology, protein biochemistry, and structural biology is essential for comprehensive characterization.

How might ORFJ be involved in the broader context of bacterial-phage coevolution?

The study of ORFJ in retron EC67 can provide insights into the broader context of bacterial-phage coevolution:

• Evolutionary analysis:

  • Compare ORFJ sequences across different bacterial strains

  • Identify signs of positive selection or rapid evolution

  • Correlate sequence diversity with exposure to different phage populations

  • Construct phylogenetic trees to understand evolutionary history

• Host range determinants:

  • Test if ORFJ confers resistance to specific phage types

  • Identify phage proteins that trigger or are recognized by ORFJ

  • Determine if phages have evolved to counter ORFJ's function

  • Compare with other retron systems and their phage targets

• Horizontal gene transfer:

  • Analyze genomic context of retron EC67 for signs of horizontal acquisition

  • Identify potential mobile genetic elements associated with ORFJ

  • Study distribution of ORFJ homologs across bacterial species

  • Assess if retron EC67 can be transferred between bacterial strains

• Integration with other defense systems:

  • Investigate potential functional overlap with CRISPR-Cas, restriction-modification, or other defense systems

  • Test if ORFJ works synergistically with other immune mechanisms

  • Determine if phages that evade ORFJ are still susceptible to other defenses

  • Construct a comprehensive model of layered defense strategies

• Experimental evolution:

  • Subject bacteria expressing ORFJ to continuous phage challenge

  • Monitor changes in both bacterial and phage genomes

  • Identify mutations that enhance or compromise ORFJ function

  • Track the emergence of phage counter-defense mechanisms

Understanding ORFJ's role in this evolutionary arms race could reveal fundamental principles of host-parasite coevolution and inform the development of new antimicrobial strategies and biotechnological applications.

What are common issues when working with the ORFJ antibody and how can they be resolved?

When working with the Putative uncharacterized protein ORFJ in retron EC67 antibody, researchers may encounter several common issues:

For optimal results:

• Store the antibody at -20°C or -80°C and avoid repeated freeze-thaw cycles

• Pre-adsorb the antibody with lysate from E. coli strains lacking retron EC67

• Optimize the antibody dilution specifically for your experimental system

• Include appropriate positive and negative controls in each experiment

How can researchers properly validate results obtained using the ORFJ antibody?

To ensure the validity of results obtained with the ORFJ antibody, researchers should implement a comprehensive validation strategy:

• Specificity verification:

  • Compare signals between retron EC67-containing strains and retron-free strains

  • Perform antigen competition by pre-incubating the antibody with purified ORFJ protein

  • Use multiple detection methods (e.g., Western blot, ELISA, immunofluorescence)

  • Sequence verify all bacterial strains used in experiments

• Technical validation:

  • Include loading controls for all blots (e.g., anti-DnaK antibody)

  • Run biological and technical replicates (minimum n=3)

  • Quantify band intensity using appropriate software

  • Perform statistical analysis to determine significance of results

• Complementary approaches:

  • Verify key findings using alternative methods (e.g., mass spectrometry)

  • Generate tagged versions of ORFJ and detect with tag-specific antibodies

  • Create ORFJ knockout strains and confirm absence of signal

  • Use RNA interference or CRISPR-based approaches to reduce ORFJ expression

• Results reporting:

  • Include full blots with molecular weight markers in publications

  • Specify exact antibody dilutions, incubation times, and detection methods

  • Disclose any image processing performed on blots

  • Provide detailed methods to ensure reproducibility

Proper validation is crucial for antibodies targeting putative uncharacterized proteins like ORFJ, as their specificity may be more difficult to establish compared to well-characterized proteins.

How does ORFJ in retron EC67 compare to ORFJ-like proteins in other retron systems?

A comparative analysis of ORFJ with similar proteins in other retron systems reveals important insights:

ORFJ appears to be somewhat unique among retron accessory proteins, particularly in its potential DNA methylation activity. While many retrons have been classified into 13 different types based on their genetic structure and accessory proteins , retron EC67 represents a distinct lineage with specialized functions.

The diversity of accessory proteins across retron systems suggests that they have evolved different mechanisms for defense against phages. For example:

• Retron EC78 (Eco7) uses PtuA and PtuB to degrade bacterial tRNA^Tyr during phage infection

• ORFJ in retron EC67 may function through DNA methylation

• Other retrons may employ nuclease activity or disrupt specific cellular processes

This functional diversity reflects the ongoing evolutionary arms race between bacteria and phages, with each retron system adapting to counter specific phage infection strategies.

What insights can cross-species analysis of retron systems provide about ORFJ function?

Cross-species analysis of retron systems can provide several valuable insights about ORFJ function:

• Evolutionary conservation:

  • ORFJ-like proteins appear to be found primarily in Escherichia and closely related genera

  • The association with retron elements suggests acquisition through horizontal gene transfer

  • Conservation patterns may indicate functionally important residues

• Contextual genomic analysis:

  • Retron EC67 has been found integrated into prophages related to coliphage 186

  • The retron replaces approximately 180 bp of DNA between the phage cohesive end site (cos) and the transcription terminator of a phage DNA-packaging gene

  • This integration pattern is consistent with other retrons and suggests a potential mechanism for retron transposition

• Functional diversification:

  • Various retron systems have evolved diverse effector mechanisms

  • ORFJ's potential DNA methylation activity represents one strategy in this diverse arsenal

  • The methylation activity may protect host DNA while targeting phage DNA

• Host-phage interaction dynamics:

  • Retron EC67 appears to be triggered by phage proteins involved in DNA degradation (DenB, protein A1)

  • ORFJ may play a role in sensing these phage proteins or in the downstream defense response

  • The specificity for certain phages suggests coevolution with particular phage types

• Anti-defense mechanisms:

  • Some phages have evolved specific anti-retron mechanisms

  • The Rad protein from phage ΦSP15 can degrade retron ncRNA to prevent further synthesis of retron

  • Future studies may reveal if phages have specific countermeasures against ORFJ

This cross-species comparative approach highlights how retron systems represent a diverse array of bacterial defense strategies, with ORFJ potentially representing a unique methylation-based defense mechanism against phage infection.