PET117 Antibody

What is PET117 and what is its cellular function?

PET117 is a chaperone protein involved in complex IV assembly that plays a crucial role in the regulation of mitochondria-encoded cytochrome c oxidase 1 (COX1) protein synthesis in human cells . It belongs to the PET117 protein family and has been associated with Mitochondrial complex IV deficiency . The protein is predominantly localized in the mitochondria, specifically as a matrix protein peripherally associated with the mitochondrial inner membrane .

Studies using yeast models have demonstrated that cells lacking Pet117 are respiration-compromised due to cytochrome c oxidase (CcO) defects . When PET117 is deleted, cells show normal growth on fermentable glucose-containing medium but fail to propagate on respiratory medium containing glycerol and lactate, indicating its critical role in mitochondrial respiration . The protein's evolutionary conservation across species including mouse, bovine, zebrafish, chimpanzee and chicken highlights its fundamental importance in cellular metabolism .

What are the key structural and biochemical characteristics of PET117?

PET117 is notably expressed in multiple human tissues, with significant expression observed in the caudate, urinary bladder, and appendix . Alternative names for this protein include PET117 homolog, alternative protein CSRP2BP, and protein PET117 homolog, mitochondrial . The protein has been characterized as only loosely associated with mitochondrial membranes, as evidenced by its recovery in the soluble fraction following sodium carbonate treatment at high pH .

What applications are PET117 antibodies commonly used for?

PET117 antibodies are primarily utilized in several key applications in research settings:

These antibodies are most commonly employed in immunohistochemistry experiments to study the distribution and localization of PET117 in various tissues . Additionally, they are valuable for Western blot analysis to detect PET117 protein levels in cell lysates, with HepG2 cells being a validated positive control . The antibodies can help researchers investigate the role of PET117 in mitochondrial complex IV assembly and function, particularly in the context of respiratory chain disorders.

How should PET117 antibodies be stored and handled for optimal results?

For optimal performance and longevity, PET117 antibodies should be stored at -20°C where they typically remain stable for one year after shipment . The antibodies are generally supplied in PBS buffer containing 0.02% sodium azide and 50% glycerol at pH 7.3 . This formulation helps maintain antibody integrity during freeze-thaw cycles.

For long-term storage, it's advisable to create small aliquots to minimize repeated freeze-thaw cycles, although some suppliers indicate that aliquoting may be unnecessary for -20°C storage of certain PET117 antibody preparations . When handling the antibody, standard laboratory safety precautions should be observed, particularly due to the presence of sodium azide, which is toxic and can form explosive compounds with heavy metals found in laboratory plumbing.

Before experimental use, antibodies should be centrifuged briefly to collect contents at the bottom of the tube and kept on ice during experimental procedures. Optimization of antibody concentration for each specific application and cell/tissue type is essential for obtaining reliable results.

How does PET117 regulate cytochrome c oxidase assembly?

PET117 functions as a critical assembly factor for cytochrome c oxidase (Complex IV) in the mitochondrial respiratory chain. Research in yeast models has demonstrated that Pet117 couples heme a synthase activity to cytochrome c oxidase assembly . In Pet117-deficient cells, the steady-state levels of core CcO subunits Cox1, Cox2, and Cox3 are dramatically decreased, while components of other respiratory complexes remain largely unaffected .

Blue native PAGE analysis of respiratory complexes from Pet117-deficient mitochondria reveals that CcO/bc1 supercomplexes (with stoichiometries III₂IV₂ and III₂IV in yeast) are dramatically impaired due to the loss of CcO . These cells accumulate dimeric Complex III, which is the expected result when Complex IV is absent . This suggests that PET117 plays a specific role in the assembly or stability of Complex IV rather than having a general effect on all respiratory complexes.

The molecular mechanism appears to involve PET117's role in regulating mitochondria-encoded cytochrome c oxidase 1 (COX1) protein synthesis . COX1 forms the catalytic core of Complex IV, and its proper synthesis and incorporation are essential for the assembly of the entire complex. PET117 may function as a chaperone that facilitates this process, ensuring the correct assembly of functional cytochrome c oxidase.

What experimental approaches can effectively detect PET117-protein interactions?

To investigate PET117 interactions with other mitochondrial proteins, researchers can employ several complementary techniques:

• Co-immunoprecipitation (Co-IP): Using anti-PET117 antibodies (such as the rabbit polyclonal antibody 31066-1-AP) to pull down PET117 along with its interacting partners . This approach can be optimized using mild detergents to preserve protein-protein interactions while ensuring efficient extraction from mitochondrial membranes.

• Proximity-based labeling: Techniques such as BioID or APEX can be used by fusing PET117 to a biotin ligase or peroxidase, respectively, allowing for biotinylation of proximal proteins that can then be identified by mass spectrometry.

• Crosslinking mass spectrometry: Chemical crosslinking followed by mass spectrometry can capture transient interactions between PET117 and other mitochondrial proteins.

• Yeast two-hybrid assays: Though limited by potential false positives, this system can provide initial insights into direct PET117 interactors.

• Fluorescence microscopy with subcellular fractionation: Combining immunofluorescence using PET117 antibodies with markers for different mitochondrial compartments can reveal PET117's precise submitochondrial localization and potential co-localization with other proteins .

When analyzing results, it's important to validate interactions using multiple approaches and to consider the loose association of PET117 with mitochondrial membranes, as demonstrated by its recovery in the soluble fraction following sodium carbonate treatment at high pH .

What are the best troubleshooting strategies for PET117 antibody experiments?

When encountering issues with PET117 antibody experiments, consider these methodological troubleshooting approaches:

For Western Blot Issues:

For PET117 specifically, given its small size (9.2 kDa theoretical, 10 kDa observed) , use appropriate gel percentages (15-20%) for optimal resolution in the low molecular weight range. Consider using HepG2 cells as a positive control, as they have been validated for PET117 detection .

For Immunohistochemistry Issues:

Optimize antigen retrieval methods, as mitochondrial proteins often require specific retrieval conditions due to their localization. Titrate antibody concentrations carefully within the recommended 1:50-1:200 range . Include appropriate controls, including tissues known to have high PET117 expression such as caudate, urinary bladder, and appendix .

If non-specific staining occurs, increasing blocking steps with both protein blockers and appropriate serum can help improve specificity. When analyzing results, remember that PET117's mitochondrial localization should produce a characteristic punctate or reticular staining pattern consistent with mitochondrial distribution.

How does PET117 deficiency affect mitochondrial respiration at the molecular level?

PET117 deficiency profoundly impacts mitochondrial respiration through its specific effect on cytochrome c oxidase (Complex IV). Research has demonstrated that Pet117-deficient yeast cells exhibit normal growth on fermentable glucose-containing medium but completely fail to propagate on respiratory medium containing glycerol and lactate . This respiratory growth defect corresponds with the complete absence of CcO-specific activity in mitochondria isolated from Pet117-deficient cells compared to wild-type controls .

At the molecular level, several key impacts have been observed:

• Respiratory complex assembly: Blue native PAGE analysis reveals that in Pet117-deficient cells, the dimeric and monomeric forms of Complex V (ATP synthase) and Complex II remain intact, while CcO/bc₁ supercomplexes are dramatically impaired specifically due to the loss of CcO .

• Subunit stability: The steady-state levels of core CcO subunits Cox1, Cox2, and Cox3 are dramatically decreased in Pet117-deficient mitochondria, whereas levels of other respiratory complex components (such as the cytochrome bc₁ complex component Rip1) remain unaffected .

• Compensatory changes: Pet117-deficient cells accumulate dimeric Complex III . This accumulation is the expected result of the specific loss of Complex IV, as Complex III dimers normally associate with Complex IV to form respiratory supercomplexes.

These findings demonstrate that PET117 plays a highly specific role in the assembly and function of Complex IV without substantially affecting other respiratory complexes. The mechanism appears to involve PET117's chaperone activity in the regulation of mitochondria-encoded cytochrome c oxidase 1 (COX1) protein synthesis , which is critical for the assembly of the entire complex.

What are the optimal protocols for using PET117 antibodies in Western blot analysis?

For obtaining optimal results when using PET117 antibodies in Western blot analyses, researchers should follow this detailed protocol:

Sample Preparation:

• Extract total protein from cells/tissues using a buffer containing protease inhibitors

• Determine protein concentration using Bradford or BCA assay

• Prepare 10-30 µg of protein per lane mixed with Laemmli buffer containing reducing agent

• Heat samples at 95°C for 5 minutes to denature proteins

Gel Electrophoresis:

• Use 15-20% polyacrylamide gels due to PET117's small size (9.2 kDa theoretical, 10 kDa observed)

• Include HepG2 cell lysate as a positive control

• Run gel at 100-120V until dye front reaches bottom

Transfer:

• Use PVDF membrane (0.2 µm pore size preferred for small proteins)

• Transfer at 100V for 60 minutes in cold transfer buffer containing 20% methanol

• Verify transfer efficiency with Ponceau S staining

Antibody Incubation:

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

• Incubate with anti-PET117 antibody at 1:500-1:3000 dilution in blocking buffer overnight at 4°C

• Wash 3x10 minutes with TBST

• Incubate with appropriate HRP-conjugated secondary antibody (typically anti-rabbit) for 1 hour at room temperature

• Wash 3x10 minutes with TBST

Detection:

• Apply ECL substrate and visualize using film or digital imaging

• Expect a band at approximately 10 kDa

This protocol should be optimized for specific laboratory conditions, and researchers should be aware that the observed molecular weight may differ slightly from the calculated molecular weight due to protein structure or post-translational modifications.

How can I validate the specificity of PET117 antibodies in my experiments?

Validating antibody specificity is crucial for ensuring reliable research results. For PET117 antibodies, consider implementing these validation methods:

• Genetic validation:

  • Use PET117 knockout or knockdown models (CRISPR-Cas9, siRNA, or shRNA) as negative controls

  • Compare signal between wild-type and PET117-depleted samples in Western blot and immunostaining

• Peptide competition assay:

  • Pre-incubate the antibody with excess immunizing peptide

  • Compare results with and without peptide competition (signal should be reduced or eliminated with peptide)

• Orthogonal detection methods:

  • Compare results using multiple antibodies targeting different epitopes of PET117

  • Correlate protein detection with mRNA expression (qPCR or RNA-seq data)

• Recombinant protein control:

  • Use purified recombinant PET117 protein as a positive control

  • Compare mobility with endogenous protein

• Subcellular fractionation:

  • Verify that PET117 is detected primarily in mitochondrial fractions rather than other cellular compartments

  • Confirm appropriate localization pattern (mitochondrial matrix with loose membrane association)

• Cross-reactivity assessment:

  • Test antibody reactivity across multiple species if working with non-human models

  • PET117 orthologs have been reported in mouse, bovine, zebrafish, chimpanzee and chicken species

Antibody validation should be performed for each new lot of antibody and for each experimental system (cell type, tissue, or species) being studied. Proper validation ensures that experimental observations genuinely reflect PET117 biology rather than non-specific or off-target effects.

What considerations are important when designing PET117 immunoprecipitation experiments?

When designing immunoprecipitation (IP) experiments to study PET117 and its interaction partners, several important considerations must be addressed:

• Buffer composition:

  • Use buffers that preserve mitochondrial protein interactions while efficiently extracting PET117

  • Consider that PET117 is loosely associated with mitochondrial membranes , so harsh detergents may disrupt important interactions

  • Start with gentle non-ionic detergents like digitonin (0.5-1%) or NP-40/IGEPAL (0.5%)

  • Include protease inhibitors to prevent degradation during the procedure

• Antibody selection:

  • Use well-validated PET117 antibodies with proven specificity

  • Consider using antibodies that have been specifically validated for immunoprecipitation, not just Western blotting

  • Both N-terminal and C-terminal targeting antibodies may be useful to compare results

• Controls:

  • Include IgG isotype control to identify non-specific binding

  • Consider using PET117-depleted cells as a negative control

  • Include input samples (pre-IP lysate) to assess IP efficiency

  • Use reciprocal IP with antibodies against suspected interaction partners to confirm interactions

• Crosslinking considerations:

  • For transient interactions, consider using crosslinking agents like formaldehyde or DSP

  • Crosslinking may be particularly important for PET117 given its role as a chaperone protein

  • Optimize crosslinking conditions to balance capture of protein complexes with epitope accessibility

• Elution and analysis:

  • Consider native elution methods if downstream functional assays are planned

  • For mass spectrometry analysis, ensure compatibility of buffers and elution conditions

  • When analyzing co-immunoprecipitated proteins, focus on mitochondrial proteins involved in cytochrome c oxidase assembly

Given PET117's small size (9.2 kDa) , be aware that it may be masked by antibody chains on Western blots following IP. Consider using antibodies conjugated to beads or crosslinked to beads to minimize antibody chain interference in downstream analyses.

How can PET117 antibodies be used to study mitochondrial disorders?

PET117 antibodies offer valuable tools for investigating mitochondrial disorders, particularly those involving cytochrome c oxidase deficiency. Strategic applications include:

• Diagnostic biomarker development:

  • PET117 has been associated with Mitochondrial complex IV deficiency

  • Antibodies can be used to assess PET117 protein levels in patient samples compared to healthy controls

  • Immunohistochemistry on patient tissues can reveal alterations in PET117 expression or localization

• Pathophysiological mechanisms:

  • Western blot analysis can quantify changes in PET117 levels across different tissues affected by mitochondrial disease

  • Co-immunoprecipitation can identify altered protein interactions in disease states

  • Immunofluorescence microscopy can reveal changes in mitochondrial morphology and PET117 distribution

• Therapeutic response monitoring:

  • Following therapeutic interventions, PET117 antibodies can be used to monitor restoration of normal protein levels or localization

  • Changes in PET117-associated protein complexes can be assessed as markers of mitochondrial function recovery

• Model system validation:

  • When creating cell or animal models of mitochondrial disorders, PET117 antibodies can verify that the models recapitulate key molecular features of human disease

  • The dramatic decrease in Cox1, Cox2, and Cox3 levels observed in Pet117-deficient models provides specific molecular markers that can be monitored

• Correlation studies:

  • PET117 protein levels can be correlated with cytochrome c oxidase activity measurements to establish relationships between protein expression and functional outcomes

  • Such correlations may help identify patient subgroups or predict disease progression

When applying these approaches, researchers should consider tissue-specific expression patterns of PET117, with notable expression in the caudate, urinary bladder, and appendix , which may guide the selection of appropriate tissues for analysis in specific disorders.

What are emerging techniques for studying PET117 function in live cells?

Cutting-edge techniques for studying PET117 function in live cells provide dynamic insights that complement traditional fixed-cell approaches. Several promising methodologies include:

• Fluorescent protein tagging and live imaging:

  • CRISPR-Cas9 knock-in of fluorescent tags to endogenous PET117

  • Time-lapse microscopy to monitor PET117 dynamics during mitochondrial stress or biogenesis

  • Combined with mitochondrial markers to correlate PET117 behavior with mitochondrial morphology changes

• Optogenetic approaches:

  • Light-inducible protein degradation systems (e.g., OptoDegrade) to achieve temporal control over PET117 levels

  • Monitoring real-time consequences of acute PET117 depletion on mitochondrial function and morphology

  • Comparing these effects with traditional knockout approaches to distinguish acute versus adaptive responses

• FRET/BRET biosensors:

  • Development of Förster resonance energy transfer (FRET) or bioluminescence resonance energy transfer (BRET) biosensors to monitor PET117 interactions with other proteins in real-time

  • These approaches can reveal transient interactions that might be missed by biochemical approaches

• Mitochondrial respiration measurements in live cells:

  • Seahorse XF analysis to correlate PET117 manipulation with real-time oxygen consumption rates

  • Measurement of mitochondrial membrane potential using voltage-sensitive dyes in cells with altered PET117 expression

• Genetically-encoded redox sensors:

  • Integration of sensors like roGFP or HyPer with PET117 studies to monitor changes in mitochondrial redox state

  • This approach can link PET117 function to redox homeostasis in mitochondria

• Single-cell proteomics approaches:

  • Emerging mass cytometry methods to correlate PET117 levels with other proteins at single-cell resolution

  • This can reveal cell-to-cell heterogeneity in mitochondrial composition and function

These advanced approaches will help bridge the gap between structural studies of PET117 and physiological outcomes in relevant cellular contexts. Since PET117 is involved in cytochrome c oxidase assembly and has been associated with mitochondrial disorders , these techniques may provide novel insights into disease mechanisms and potential therapeutic approaches.