ATP5S Antibody

What is ATP5S and why is it important in mitochondrial function?

ATP5S, also known as ATP synthase-coupling factor B or factor B, is a 215 amino acid mitochondrial inner membrane protein belonging to the ATP synthase subunits family. It plays a critical role in the regulation of mitochondrial membrane ATP synthase and is necessary for H+ conduction through the proton channel. This subunit is essential for energy transduction in ATP synthase complexes, making it crucial for cellular ATP production through oxidative phosphorylation. The ATP5S gene is highly conserved across species including chimpanzee, mouse, rat, chicken, and zebrafish, highlighting its evolutionary importance in energy metabolism . Understanding ATP5S function can provide insights into mitochondrial diseases and energy metabolism disorders.

What should researchers consider when selecting an ATP5S antibody?

When selecting an ATP5S antibody for research applications, consider these critical factors:

• Epitope specificity: Determine whether the antibody targets a specific region (N-terminal, C-terminal, or internal regions). Different epitopes may affect accessibility depending on protein conformation or interactions .

• Species reactivity: Verify cross-reactivity with your experimental model. Many ATP5S antibodies show reactivity with human and mouse samples, with some also detecting rat and pig orthologs. The highest antigen sequence identity is approximately 73% for mouse and 72% for rat compared to human ATP5S .

• Validated applications: Confirm the antibody has been validated for your specific application (Western blot, ELISA, ICC, etc.) .

• Clonality: Most available ATP5S antibodies are polyclonal, typically raised in rabbits. Polyclonal antibodies often provide stronger signals by recognizing multiple epitopes but may have batch-to-batch variation .

• Purification method: Affinity-purified antibodies typically offer better specificity. Most commercial ATP5S antibodies are purified using epitope-specific immunogen affinity chromatography .

How is ATP5S protein typically detected in experimental systems?

ATP5S protein detection typically employs these methodologies:

For optimal detection, researchers should note that ATP5S has been successfully detected in human cell lines such as HL-60 and K-562, as well as in human placenta tissue . The typical molecular weight observed on Western blots is approximately 23 kDa, which differs slightly from the calculated molecular weight of 25 kDa based on amino acid sequence . This discrepancy may reflect post-translational modifications or protein processing in vivo.

What are the optimal sample preparation methods for ATP5S detection in mitochondrial fractions?

For optimal detection of ATP5S in mitochondrial fractions, researchers should implement a careful sample preparation protocol:

• Mitochondrial isolation: Use established differential centrifugation methods with sucrose gradients to obtain purified mitochondria. For adherent cells, begin with trypsinization followed by cell lysis using a Dounce homogenizer in isotonic buffer (250mM sucrose, 10mM HEPES, 1mM EDTA, pH 7.4).

• Membrane protein extraction: Since ATP5S is a mitochondrial inner membrane protein, use gentle detergents that preserve protein structure while effectively solubilizing membrane proteins. A recommended approach is to use 1% digitonin or 0.5% n-dodecyl β-D-maltoside (DDM) in PBS with protease inhibitors at 4°C for 30-60 minutes with gentle agitation.

• Protein preservation: Include a cocktail of protease inhibitors (PMSF, leupeptin, aprotinin, pepstatin A) to prevent degradation. ATP5S appears stable in standard conditions, but for optimal preservation, process samples immediately and maintain at 4°C throughout preparation .

• Buffer considerations: Use buffers that maintain mitochondrial integrity. PBS with 0.02% sodium azide and 50% glycerol at pH 7.3 is commonly used for storage of ATP5S antibodies and may be compatible with immunoprecipitation experiments .

• Sample loading: For Western blot analysis, load 20-50μg of mitochondrial protein per lane and use a 12-15% SDS-PAGE gel for optimal resolution of the 23 kDa ATP5S protein.

How should researchers validate the specificity of ATP5S antibodies in their experimental systems?

Validating ATP5S antibody specificity is essential for obtaining reliable research data. A comprehensive validation approach includes:

• Positive and negative controls: Use known positive samples (HL-60 cells, K-562 cells, human placenta tissue) where ATP5S expression has been confirmed . For negative controls, consider using CRISPR/Cas9 ATP5S knockout cells or siRNA-mediated knockdown.

• Peptide competition assay: Pre-incubate the antibody with excess immunizing peptide before application to demonstrate signal specificity. If the signal disappears after peptide competition, this confirms antibody specificity.

• Cross-species validation: If working with non-human models, verify reactivity using samples from relevant species. Commercial ATP5S antibodies typically show cross-reactivity with mouse (73% sequence identity) and rat (72% sequence identity) proteins .

• Multiple antibody comparison: Use antibodies targeting different epitopes of ATP5S to confirm consistent detection patterns.

• Molecular weight verification: Confirm that the detected protein band appears at the expected molecular weight of approximately 23 kDa, which is the observed molecular weight for ATP5S despite its calculated molecular weight of 25 kDa .

• Subcellular fractionation: Verify that the antibody predominantly detects ATP5S in mitochondrial fractions rather than other cellular compartments, consistent with its known localization.

What special considerations should be taken when studying ATP5S in different cellular contexts?

When studying ATP5S across different cellular contexts, researchers should consider the following factors:

• Tissue-specific expression levels: ATP5S expression can vary between tissues based on their metabolic activity and mitochondrial content. High-energy demanding tissues like heart, muscle, and brain typically show higher expression levels.

• Cellular stress response: Oxidative stress, hypoxia, and other cellular stressors can affect mitochondrial function and potentially alter ATP5S expression or localization. Include appropriate stress controls when studying cells under various conditions.

• Mitochondrial dynamics: Changes in mitochondrial fusion/fission events and mitophagy can affect the detection of mitochondrial proteins including ATP5S. Consider analyzing mitochondrial morphology alongside ATP5S detection.

• Cell proliferation state: Rapidly proliferating cells may have different metabolic requirements affecting ATP synthase complex regulation. Compare ATP5S levels between proliferating and quiescent cells when relevant.

• Species differences: Despite high conservation, there are sequence differences between species (e.g., 73% identity between human and mouse) . These differences may affect antibody binding efficiency and experimental interpretation when comparing across species.

• Experimental conditions: For immunofluorescence or immunohistochemistry, fixation methods can significantly impact epitope accessibility. Test both paraformaldehyde and methanol fixation to determine optimal conditions for ATP5S detection.

What are common issues in ATP5S antibody-based detection and how can they be resolved?

Researchers frequently encounter several challenges when working with ATP5S antibodies:

When optimizing Western blot protocols specifically, a dilution series ranging from 1:1000 to 1:4000 is recommended for most ATP5S antibodies, with initial testing at 1:2000 for standardized protein loads . For ELISA applications, much higher dilutions (1:10,000) are typically effective .

How can researchers optimize immunoprecipitation protocols for ATP5S and its interaction partners?

Optimizing immunoprecipitation (IP) of ATP5S requires special considerations due to its membrane localization and complex formation:

• Lysis buffer selection: Use mild detergents that preserve protein-protein interactions while effectively solubilizing membrane proteins. Start with 1% digitonin or 0.5% n-dodecyl β-D-maltoside (DDM) in a buffer containing 150mM NaCl, 50mM Tris-HCl (pH 7.4), 1mM EDTA, and protease inhibitors.

• Cross-linking consideration: For transient or weak interactions, consider using reversible cross-linkers like DSP (dithiobis[succinimidylpropionate]) prior to cell lysis to stabilize protein complexes.

• Pre-clearing step: To reduce non-specific binding, pre-clear lysates with protein A/G beads for 1 hour at 4°C before adding the ATP5S antibody.

• Antibody selection: Choose antibodies validated for immunoprecipitation. Polyclonal antibodies often perform better for IP than monoclonals due to recognition of multiple epitopes.

• Negative controls: Include an isotype control (normal rabbit IgG) and potentially an ATP5S-depleted sample as negative controls.

• Washing conditions: Use progressively stringent washing buffers to remove non-specific interactions while preserving specific ones. Begin with lysis buffer and increase salt concentration slightly in subsequent washes.

• Elution strategies: For co-IP experiments analyzing interaction partners, consider native elution with competing peptides rather than denaturing elution with SDS to preserve complex integrity.

• Verification of results: Confirm pulled-down proteins by both Western blot and mass spectrometry to identify novel interaction partners within the ATP synthase complex.

What factors affect ATP5S antibody performance in different experimental conditions?

Several factors significantly impact ATP5S antibody performance across different experimental platforms:

• Buffer composition: Storage buffers containing 50% glycerol help maintain antibody stability. Working buffers with 0.02% sodium azide prevent microbial contamination but may interfere with HRP-based detection systems .

• Temperature sensitivity: While ATP5S antibodies are generally stable at -20°C for up to one year, repeated freeze-thaw cycles can degrade performance. Aliquot antibodies upon receipt to minimize these cycles .

• Epitope accessibility: The specific region of ATP5S targeted by the antibody affects performance in different applications. Internal region-targeting antibodies may work better for denatured proteins (Western blot), while surface-exposed epitope antibodies might perform better in native applications.

• Fixation methods: For immunocytochemistry or immunohistochemistry applications, the fixation method significantly impacts epitope preservation. Test both paraformaldehyde (4%, 10 minutes) and methanol (-20°C, 5 minutes) fixation protocols.

• Blocking reagents: Optimization of blocking conditions is essential. BSA-containing buffers may improve signal-to-noise ratio compared to milk-based blockers for some ATP5S antibodies, especially in fluorescence applications.

• Incubation times: Primary antibody incubation time may need extension for membrane proteins like ATP5S. Consider overnight incubation at 4°C rather than standard 1-2 hour protocols at room temperature.

• Secondary antibody selection: Anti-rabbit IgG secondary antibodies with minimal cross-reactivity to other species should be selected, as most ATP5S antibodies are rabbit-derived .

How can ATP5S antibodies be utilized in studies of mitochondrial disorders and disease models?

ATP5S antibodies serve as valuable tools in investigating mitochondrial disorders through multiple advanced applications:

• Differential expression analysis: Quantify ATP5S levels in patient-derived samples versus healthy controls to identify alterations associated with mitochondrial diseases. Western blot analysis using validated ATP5S antibodies at 1:1000-1:4000 dilutions can reliably detect expression differences .

• Tissue-specific investigations: Employ immunohistochemistry to examine ATP5S distribution patterns across affected tissues in disease models, particularly in high-energy demanding tissues like cardiac muscle, brain, and skeletal muscle where mitochondrial dysfunction has pronounced effects.

• Interaction partner shifts: Use co-immunoprecipitation with ATP5S antibodies to identify altered protein-protein interactions within the ATP synthase complex in disease states. This approach can reveal mechanistic changes in complex assembly or regulation.

• Post-translational modification profiling: Combine ATP5S immunoprecipitation with mass spectrometry to detect disease-associated changes in post-translational modifications that may affect function.

• Super-resolution microscopy: Utilize immunofluorescence with ATP5S antibodies in techniques like STORM or STED microscopy to visualize nanoscale changes in mitochondrial morphology and ATP5S distribution in disease models.

• Drug screening applications: Develop high-content screening assays using ATP5S antibodies to identify compounds that normalize ATP5S levels or localization in disease models as potential therapeutic candidates.

• Patient stratification: Explore whether ATP5S expression patterns or modifications correlate with disease severity or progression, potentially establishing ATP5S as a biomarker for certain mitochondrial disorders.

What are the current techniques for studying ATP5S in the context of mitochondrial ATP synthase complex assembly?

Investigating ATP5S within the context of ATP synthase complex assembly requires sophisticated methodological approaches:

• Blue Native PAGE (BN-PAGE): This technique preserves protein-protein interactions and can separate intact ATP synthase complexes. Follow with Western blotting using ATP5S antibodies to determine its incorporation into assembled complexes versus free subunits.

• Proximity labeling methods: Employ BioID or APEX2 proximity labeling by generating ATP5S fusion constructs to identify neighboring proteins during complex assembly. This provides temporal information about the assembly process.

• CRISPR/Cas9 genome editing: Generate ATP5S knockout or knockdown models to study the consequences on ATP synthase assembly. Rescue experiments with mutant versions can identify critical regions for assembly.

• Pulse-chase experiments: Combine radioactive labeling or photo-convertible fluorescent tags with immunoprecipitation using ATP5S antibodies to track the kinetics of ATP5S incorporation into the ATP synthase complex.

• Cryo-electron microscopy: Use ATP5S antibodies with gold nanoparticle labeling to precisely localize ATP5S within the three-dimensional structure of the ATP synthase complex.

• Mass spectrometry-based approaches: Combine crosslinking mass spectrometry (XL-MS) with ATP5S antibody-based purification to map interaction interfaces between ATP5S and other subunits during assembly.

• Live-cell imaging: Utilize split-GFP or FRET-based approaches with ATP5S to visualize complex assembly dynamics in living cells, providing insights into the temporal aspects of assembly.

How can researchers investigate the role of ATP5S in cellular bioenergetics and metabolic regulation?

Investigating ATP5S's role in cellular bioenergetics requires integrating antibody-based detection with functional metabolic analyses:

• Seahorse XF Analysis: Measure oxygen consumption rate (OCR) and extracellular acidification rate (ECAR) in cells with modulated ATP5S expression, then correlate functional changes with ATP5S protein levels detected by immunoblotting.

• Mitochondrial membrane potential assays: Combine JC-1 or TMRM staining with ATP5S immunofluorescence to correlate ATP5S expression levels with membrane potential at the single-cell level.

• ATP production measurement: Employ luminescence-based ATP assays in conjunction with ATP5S immunoprecipitation to establish direct relationships between ATP5S function and cellular ATP levels.

• Metabolic flux analysis: Use stable isotope-labeled substrates (13C-glucose or 13C-glutamine) to track metabolic pathways, then correlate pathway activity with ATP5S expression detected by immunoblotting.

• Imaging-based approaches: Implement FLIM (Fluorescence Lifetime Imaging Microscopy) with ATP5S immunofluorescence to simultaneously visualize protein localization and measure NADH/NAD+ ratios as indicators of metabolic state.

• Single-cell analysis: Combine ATP5S immunostaining with mass cytometry (CyTOF) or single-cell RNA-seq to uncover cell-to-cell variability in ATP5S expression and its relationship to metabolic heterogeneity.

• Stress response studies: Examine how various metabolic stressors (hypoxia, nutrient deprivation, electron transport chain inhibitors) affect ATP5S expression, localization, and post-translational modifications using appropriate antibody-based detection methods.

How should researchers interpret discrepancies between ATP5S protein expression and functional ATP synthase activity?

When faced with discrepancies between ATP5S protein levels and ATP synthase functional activity, researchers should consider several interpretative frameworks:

• Post-translational regulation: ATP5S function may be regulated by modifications not detected by standard immunoblotting. Consider phosphorylation-specific antibodies or mass spectrometry analysis of immunoprecipitated ATP5S to identify regulatory modifications.

• Complex assembly efficiency: Even with normal ATP5S levels, defects in assembly of the complete ATP synthase complex could impair function. Complement ATP5S detection with analysis of other critical subunits and use Blue Native PAGE to assess intact complex formation.

• Threshold effects: Functional impairment may require substantial reduction in ATP5S levels below a certain threshold. Establish dose-response relationships using graded knockdown experiments correlated with functional assays.

• Compensatory mechanisms: Upregulation of alternative components might partially compensate for ATP5S dysfunction. Expand analysis to include related subunits or alternative energy production pathways.

• Localization versus expression: Total ATP5S protein levels may remain unchanged while mitochondrial incorporation is altered. Use subcellular fractionation and immunofluorescence to distinguish between properly localized versus mislocalized protein.

• Temporal dynamics: Consider whether acute versus chronic changes in ATP5S have different functional impacts due to adaptive responses. Time-course experiments can help resolve such discrepancies.

• Technical considerations: Ensure that antibodies are detecting all relevant forms of ATP5S, as the observed molecular weight (23 kDa) differs from the calculated weight (25 kDa), suggesting potential processing or modifications that might affect function .

What are emerging techniques for studying ATP5S function that complement antibody-based approaches?

Cutting-edge techniques that complement traditional antibody-based approaches include:

• CRISPR-based live-cell imaging: Use CRISPR-Cas9 to insert fluorescent tags at the endogenous ATP5S locus, enabling visualization of ATP5S dynamics at physiological expression levels without the need for antibodies.

• Nanobody development: Engineer camelid-derived single-domain antibodies (nanobodies) against ATP5S that can penetrate living cells and function in reducing environments where conventional antibodies fail.

• Mass spectrometry-based proteomics: Implement techniques like thermal proteome profiling (TPP) or limited proteolysis coupled to mass spectrometry (LiP-MS) to study ATP5S conformational changes without antibody-related constraints.

• Genome-wide interaction studies: Employ CRISPR screens to identify genetic modifiers of ATP5S function, revealing unexpected regulatory pathways.

• Single-molecule techniques: Apply methods like single-molecule FRET or optical tweezers to study the biophysical properties of ATP5S within the ATP synthase complex at unprecedented resolution.

• Organoid and 3D culture systems: Investigate ATP5S function in more physiologically relevant contexts than traditional cell cultures, potentially revealing tissue-specific roles.

• In situ structural biology: Use techniques like cryo-electron tomography to visualize ATP5S within intact cellular environments, providing structural insights under native conditions.

• Microfluidic approaches: Develop lab-on-a-chip systems for high-throughput analysis of ATP5S function under precisely controlled microenvironments that can mimic disease states.

How will understanding ATP5S contribute to therapeutic approaches for mitochondrial diseases?

The implications of ATP5S research for therapeutic development are significant and multifaceted:

• Biomarker development: Changes in ATP5S expression, modification, or complex incorporation could serve as diagnostic or prognostic biomarkers for mitochondrial diseases. Antibody-based assays could be developed for clinical detection of such biomarkers.

• Drug target validation: Determining the precise role of ATP5S in disease states might reveal it as a direct therapeutic target or identify downstream effectors as potential intervention points.

• Gene therapy approaches: For diseases involving ATP5S mutations, targeted gene editing or replacement strategies could be developed. Validating such approaches would rely heavily on antibody-based detection to confirm proper expression and localization.

• Small molecule screening: High-throughput screens for compounds that modulate ATP5S function or restore normal complex assembly could identify therapeutic candidates. Such screens would utilize ATP5S antibodies for readout validation.

• Mitochondrial transplantation: As experimental mitochondrial transplantation therapies advance, understanding ATP5S's role in bioenergetics will be crucial for assessment of transplant success and functional restoration.

• Personalized medicine applications: ATP5S antibody-based assays might help stratify patients based on specific mitochondrial dysfunction mechanisms, leading to more targeted therapeutic approaches.

• Metabolic intervention strategies: Detailed understanding of how ATP5S influences cellular energy metabolism could inform metabolic interventions (dietary modifications, metabolic supplements) tailored to specific mitochondrial disorders.