Anti-SPPL3 Rabbit Polyclonal Antibody

Frequently Asked Questions

What molecular weight should I expect for SPPL-3 on Western blot?

SPPL-3 (UniProt Q8TCT6) has a predicted molecular weight of approximately 56 kDa based on its 543-amino acid sequence. However, because SPPL-3 is an endoplasmic reticulum membrane protein that can undergo post-translational modifications including glycosylation, you may observe the band running slightly higher, typically between 56-65 kDa depending on cell type and glycosylation status. Some researchers report doublets reflecting differential processing. We recommend running positive control lysates from ER-rich tissues or overexpression systems alongside your samples at the 1:1000 dilution to establish the migration pattern in your specific system.

Does this SPPL-3 antibody cross-react with other signal peptide peptidase family members?

SPPL-3 belongs to a family that includes SPPL2a, SPPL2b, SPPL2c, and SPP. While this polyclonal antibody is validated for human SPPL-3, the signal peptide peptidase family shares structural homology in the catalytic aspartate motifs. We have not systematically tested cross-reactivity with other family members. If you are working in systems where multiple SPP-like proteases are expressed—particularly SPPL2a or SPPL2b in immune cells—consider running siRNA or CRISPR knockdown controls specific to SPPL3 to confirm that your observed band corresponds to SPPL-3 rather than a related isoform.

What sample preparation works best for detecting endogenous SPPL-3 by Western blot?

Because SPPL-3 is an ER-resident intramembrane protease, efficient extraction requires detergent-based lysis buffers that solubilize membrane proteins. RIPA buffer or similar formulations containing 1% NP-40 or Triton X-100 work reliably. Avoid dilute or mild lysis conditions that preferentially extract cytosolic proteins. For enriched detection, some groups fractionate microsomes or ER membranes before lysis, though whole-cell lysates from ER-rich cell types (hepatocytes, secretory cells, or transfected HEK293) typically yield adequate signal at the recommended 1:1000 dilution. Load 20-40 µg total protein per lane as a starting point.

Which human cell lines or tissues express high levels of SPPL-3 for positive controls?

SPPL-3 is widely expressed but levels vary. Liver, pancreas, and secretory epithelial tissues show relatively high expression due to robust ER networks and active glycoprotein biosynthesis. For cell culture controls, HEK293, HeLa, and HepG2 lines express detectable endogenous SPPL-3 by Western blot, though signal intensity depends on passage and culture conditions. Transfected overexpression lysates provide the strongest positive control when optimizing the assay. Conversely, SPPL3 knockout or knockdown cell lines, if available in your lab or via repositories, serve as essential negative controls to confirm antibody specificity, given the potential for cross-reactivity within the SPP family.

Can this rabbit polyclonal SPPL-3 antibody detect mouse or rat protein?

This antibody is validated for human SPPL-3. Mouse and rat SPPL-3 orthologs share approximately 85-90% sequence identity with human, suggesting potential cross-reactivity, but we have not formally validated performance in these species. If you plan to use mouse or rat samples, we recommend testing the antibody at 1:1000 dilution alongside a human positive control. Check for a band at the expected molecular weight (approximately 56 kDa) and confirm specificity using Sppl3 knockout tissue if available. Some researchers have reported success with rodent samples, but optimal dilution and signal strength may require empirical titration.

Is this SPPL-3 antibody suitable for immunofluorescence or immunohistochemistry?

Triple Point Biologics antibodies are broadly validated for Western blot applications. This rabbit polyclonal should be compatible with IHC and IF for detecting SPPL-3 in fixed cells or tissue sections, given its ER localization. For IF, start with a 1:100 to 1:200 dilution and expect reticular, perinuclear staining consistent with ER morphology. Antigen retrieval may improve epitope accessibility in paraffin-embedded tissues. Because SPPL-3 expression can be modest in some cell types, include appropriate positive and negative controls and consider co-staining with ER markers like calnexin or PDI to confirm localization.

How should I store this SPPL-3 antibody and what is the expected stability?

The antibody is supplied as 100 µg and should be stored at -20°C as per standard polyclonal antibody guidelines. Avoid repeated freeze-thaw cycles, which can reduce titer and increase aggregation. For frequent use, consider preparing single-use aliquots in storage buffer containing carrier protein and glycerol. Stored properly at -20°C, rabbit polyclonals typically retain activity for at least two years. Once thawed, the working dilution (1:1000 for Western blot) can be stored at 4°C with sodium azide preservative for short-term use, though we recommend preparing fresh dilutions for critical experiments to ensure optimal performance.

What are common causes of weak or absent SPPL-3 signal in Western blots?

Weak signal often stems from low endogenous expression, particularly in non-secretory cell types with limited ER mass. Confirm your cell or tissue source expresses SPPL-3 by checking RNA-seq databases or running a known positive control. Inadequate membrane solubilization is another frequent issue—ensure your lysis buffer contains sufficient detergent (1% NP-40 or equivalent). Underloading protein is also common; try increasing to 40-50 µg per lane. Finally, verify antibody handling: old aliquots or repeated freeze-thaw can diminish titer. If signal remains poor despite troubleshooting, consider membrane enrichment or longer exposures, as SPPL-3 is not an abundant protein in most cell types.