Recombinant Drosophila virilis Adenosine monophosphate-protein transferase FICD homolog (GJ12914)

What is Drosophila virilis Adenosine monophosphate-protein transferase FICD homolog (GJ12914)?

Drosophila virilis Adenosine monophosphate-protein transferase FICD homolog (GJ12914) is a protein encoded by the GJ12914 gene in Drosophila virilis. According to available sequence data, it is a 485-amino acid protein with the UniProt accession number B4LQT7 . This protein belongs to the FIC (filamentation induced by cAMP) domain-containing protein family and is predicted to function as an AMPylator, catalyzing the transfer of AMP from ATP to target proteins as a post-translational modification.

The protein's amino acid sequence contains characteristic motifs typical of FICD proteins, including a transmembrane domain at the N-terminus and the catalytic FIC domain with the conserved HPFx(D/E)GN(G/K)R motif essential for AMPylation activity .

How does the structure of FICD homolog relate to its function?

The FICD homolog contains several critical structural elements that determine its function:

• N-terminal transmembrane domain: This hydrophobic region (visible in the amino acid sequence positions 15-35) suggests localization to a cellular membrane, likely the endoplasmic reticulum (ER) .

• FIC catalytic domain: This central domain contains the conserved catalytic motif required for adenylylation/AMPylation activity. The active site geometry is specifically designed to coordinate ATP and facilitate AMP transfer to target proteins.

• Regulatory elements: The C-terminal portion likely contains regulatory elements that modulate enzymatic activity, potentially through interactions with other proteins or in response to cellular conditions.

These structural features enable the protein to function as both an AMPylator (adding AMP to proteins) and potentially as a deAMPylator (removing AMP), with the balance between these activities likely regulated by cellular stress conditions, particularly in the endoplasmic reticulum.

What are the optimal storage conditions for recombinant D. virilis FICD homolog?

Based on product information, the recommended storage conditions for maintaining optimal activity of recombinant D. virilis FICD homolog are:

• Long-term storage: -20°C or -80°C for extended preservation

• Working aliquots: 4°C for up to one week

• Storage buffer: Tris-based buffer containing 50% glycerol, specifically optimized for this protein

It's crucial to avoid repeated freeze-thaw cycles as they can significantly reduce enzymatic activity. Creating single-use aliquots before freezing is recommended for maintaining protein integrity over time .

How can I validate the enzymatic activity of recombinant D. virilis FICD homolog?

Validating the enzymatic activity of recombinant FICD homolog requires assessing its ability to transfer AMP to target proteins. Several complementary approaches can be employed:

• In vitro AMPylation assays:

  • Incubate purified recombinant FICD with putative substrates (such as BiP/GRP78 chaperones) in the presence of ATP

  • Detect AMPylation through:
    a) Radioactive assays using [α-32P]ATP followed by SDS-PAGE and autoradiography
    b) Western blotting with anti-AMP-Thr or anti-AMP-Tyr antibodies
    c) Mass spectrometry to detect the characteristic +329 Da mass shift

• Controls to include:

  • Catalytically inactive mutant (mutation in the conserved His residue of the FIC domain)

  • Substrate-only and enzyme-only reactions

  • Time course to demonstrate progressive modification

• Enzyme kinetics characterization:

  • Determine Km and Vmax values for ATP and various substrates

  • Assess effects of pH, temperature, and buffer composition on activity

How does hybrid dysgenesis in D. virilis affect research using FICD homolog?

Hybrid dysgenesis in D. virilis represents an important genetic context that researchers should consider when studying FICD homolog function. Based on available research:

• Background on hybrid dysgenesis in D. virilis:

  • Occurs when males with active transposable elements (strain 160) cross with females lacking these elements (strain 9)

  • Results in gonadal atrophy and germline stem cell death

  • Causes transposition of paternally inherited transposable element families

• Research considerations:

  • Expression patterns of FICD may differ between dysgenic and non-dysgenic backgrounds

  • Cellular stress during dysgenesis may alter FICD activity or substrate targeting

  • When using D. virilis as a model system, researchers should control for or explicitly investigate strain backgrounds

• Experimental opportunities:

  • Compare FICD expression and activity between strain 160 and strain 9 backgrounds

  • Investigate whether FICD contributes to stress responses during transposable element mobilization

  • Examine FICD activity in relation to mitotic recombination events observed during dysgenesis

Understanding this genetic context is crucial for accurate interpretation of results when using D. virilis as a model system for studying FICD function.

What are the methodological approaches for investigating FICD homolog protein-protein interactions?

Several complementary techniques can be employed to investigate the protein interaction network of D. virilis FICD homolog:

• Affinity purification coupled with mass spectrometry (AP-MS):

  • Express tagged recombinant FICD in D. virilis or D. melanogaster cell lines

  • Perform pulldown experiments followed by mass spectrometry

  • Compare interactomes between wild-type FICD and catalytically inactive mutants

  • Analyze interaction differences under normal versus stress conditions

• Proximity labeling techniques:

  • Fusion of FICD to BioID or APEX2 proximity labeling enzymes

  • Expression in relevant cellular contexts followed by biotin labeling

  • Identification of proximal proteins by streptavidin pulldown and mass spectrometry

• Yeast two-hybrid screening:

  • Using FICD as bait against D. virilis cDNA libraries

  • Validation of primary hits through secondary assays

  • Testing of interactions with known FICD partners from other species

• Co-immunoprecipitation validation:

  • Generation of antibodies against D. virilis FICD or use of epitope tags

  • Validation of key interactions in relevant cell types or tissues

  • Analysis under various cellular conditions (normal, ER stress, etc.)

These approaches would help establish the biological context of FICD function and identify potential novel regulatory partners or substrates.

How can recombinant D. virilis FICD homolog be used to study endoplasmic reticulum stress responses?

The recombinant FICD homolog provides a valuable tool for investigating ER stress response mechanisms:

• Comparative substrate profiling across stress conditions:

  • Perform in vitro AMPylation assays using cellular extracts from D. virilis cells under various stress conditions

  • Identify differentially modified proteins using mass spectrometry-based proteomics

  • Create a comprehensive map of FICD substrates under normal versus stressed conditions

• Reconstitution experiments:

  • Establish FICD-knockout D. virilis cell lines (using CRISPR-Cas9)

  • Perform rescue experiments with wild-type versus mutant FICD variants

  • Measure stress response parameters (XBP1 splicing, ATF6 activation, PERK phosphorylation)

  • Analyze how FICD activity modulates canonical UPR pathways

• Tissue-specific investigation using RNA-seq data:

  • Analyze existing RNA-seq datasets from D. virilis strains 160 and 9

  • Identify tissues with high FICD expression

  • Correlate expression patterns with stress response genes

• Interspecies comparative analysis:

  • Compare substrate specificity between D. virilis FICD and homologs from other species

  • Identify evolutionarily conserved versus species-specific targets

  • Determine if stress response mechanisms involving FICD are conserved across Drosophila species

These approaches would provide insights into how post-translational modifications by FICD contribute to cellular homeostasis during stress conditions.

What is the relationship between FICD homolog activity and transposable element mobilization during hybrid dysgenesis?

The relationship between FICD activity and transposable element (TE) mobilization presents an intriguing research direction:

• Current understanding of hybrid dysgenesis in D. virilis:

  • Hybrid dysgenesis occurs when strain 160 males (with active TEs) fertilize strain 9 females (lacking these TEs)

  • This causes widespread TE mobilization and germline stress

  • Results in mitotic recombination clusters that are associated with regions containing transposons

• Hypothesis-driven research approaches:

  • Investigate whether FICD expression changes during hybrid dysgenesis

  • Determine if ER stress pathways are activated during TE mobilization

  • Test whether FICD overexpression or knockdown modulates the severity of dysgenesis

• Experimental methodology:

  • Compare FICD expression and activity in germline tissues of dysgenic versus non-dysgenic females

  • Analyze AMPylation targets in these contexts using the recombinant protein as a tool

  • Perform genetic interaction studies between FICD and known regulators of TE activity

• Critical research questions:

  • Does cellular stress from TE mobilization alter FICD activity?

  • Could FICD-mediated AMPylation represent a protective response against TE-induced damage?

  • Are there direct or indirect interactions between FICD targets and TE regulation pathways?

This research area represents an intersection between post-translational regulation and genomic integrity maintenance systems that has not been extensively explored.

How can genome-wide approaches be used to identify the complete substrate profile of D. virilis FICD homolog?

Comprehensive identification of FICD substrates requires integrated genomic and proteomic approaches:

• Proteome-wide AMPylation profiling:

  • Develop a chemical biology approach using ATP analogs that allow "click chemistry" labeling

  • Apply to D. virilis cell extracts with recombinant FICD homolog

  • Use quantitative proteomics to identify and quantify modified proteins

  • Compare profiles with and without FICD, and between wild-type and catalytic mutants

• Genetic screening approaches:

  • Generate CRISPR interference or RNAi libraries targeting the D. virilis proteome

  • Screen for genetic interactions with FICD overexpression or knockdown

  • Identify genes that modify FICD-associated phenotypes

• Integration with high-throughput structural analysis:

  • Predict potential substrates based on structural compatibility with the FICD active site

  • Validate high-confidence candidates experimentally

  • Create a structural basis for substrate recognition

• Data integration and network analysis:

This integrated approach would provide a systems-level understanding of FICD function in D. virilis cellular physiology.

How conserved is the FICD homolog between D. virilis and D. melanogaster?

Comparative analysis of FICD homologs between Drosophila species provides evolutionary insights:

This comparative approach reveals which aspects of FICD function are under strong selective pressure versus which aspects may have evolved to accommodate species-specific requirements.

What are the experimental challenges in studying D. virilis FICD homolog compared to model organisms?

Research with D. virilis FICD presents specific challenges compared to work in more established model systems:

• Genetic tool limitations:

  • Fewer genetic resources compared to D. melanogaster

  • Limited availability of transgenic lines and mutants

  • Less established protocols for genetic manipulation

  • Solutions: Adapt CRISPR-Cas9 protocols from D. melanogaster; use recombinant protein for biochemical studies

• Genomic resource considerations:

  • The D. virilis genome is approximately 2-3 times larger than D. melanogaster

  • Contains more heterochromatic regions and repetitive elements

  • Higher recombination rates compared to D. melanogaster

  • Solutions: Use the available PacBio assembly mentioned in search results ; develop D. virilis-specific genomic resources

• Species-specific experimental conditions:

  • Optimal culture conditions differ from D. melanogaster

  • Different temperature preferences (D. virilis prefers cooler temperatures)

  • Longer development time compared to D. melanogaster

  • Solutions: Optimize experimental protocols specifically for D. virilis physiology

• Benefits of studying D. virilis despite challenges:

  • Provides evolutionary context for understanding conserved mechanisms

  • Hybrid dysgenesis system offers unique insights into genomic stress responses

  • Higher recombination rates provide advantages for certain genetic studies

  • The divergence time (~40-60 million years) from D. melanogaster allows identification of functionally constrained elements

Addressing these challenges requires adaptation of protocols and development of D. virilis-specific resources, but offers valuable comparative insights.

How can D. virilis FICD homolog studies contribute to our understanding of protein AMPylation evolution?

Studying the D. virilis FICD homolog in an evolutionary context provides several advantages for understanding the evolution of protein AMPylation:

• Evolutionary trajectory of FIC domains:

  • FIC domains are ancient protein modification modules found from bacteria to humans

  • D. virilis represents an important point in the evolutionary tree of Drosophilids

  • Comparative analysis with bacterial, other insect, and mammalian FICDs reveals conservation patterns

  • The recombinant D. virilis FICD enables biochemical comparison with homologs from diverse species

• Co-evolution with target proteins:

  • If AMPylation targets vary between species, this suggests co-evolution

  • Recombinant D. virilis FICD can be used to test cross-species substrate compatibility

  • Analysis of sequence variation in both enzyme and substrates can reveal co-evolutionary signatures

• Adaptation to ecological contexts:

  • D. virilis occupies different ecological niches than other Drosophila species

  • Testing whether FICD function is adapted to species-specific stress conditions (temperature tolerance, desiccation resistance)

  • Comparing activity profiles under various stress conditions across species

• Integration with unique genetic phenomena:

  • The hybrid dysgenesis system in D. virilis provides a unique context to study stress adaptation

  • Comparison with other dysgenesis systems (like P-M in D. melanogaster) can reveal convergent or divergent stress response mechanisms

  • Investigation of whether FICD function has adapted to manage species-specific genomic stress events