This website uses cookies to ensure you get the best experience on our website.
- Table of Contents
SP5 · Western blot design guide
Design a Western Blot for SP5
Real validated SP5 Western blot protocols, expected-band and isoform facts, troubleshooting for weak or shifted signal, and recommended anti-SP5 WB antibodies. Everything you need to plan the experiment before you commit precious samples.
Last reviewed: May 2026 · Scientific review: Boster Bio technical team
SP5 Western Blot Experimental Design Guide
Expected bands, validated protocols, controls and antibodies — the at-a-glance facts below, then the full design guide.
Must know before running
| Expected band | ~42 kDa | |
| Observed band | ~42 kDa | |
| Gel | 10–12% | |
| Negative control | siRNA / KO lysate |
Important caveats
Reasons your observed band may differ from the expected size.
| PTM | — | |
| Caveat | — | |
| Regulation | NF-κB-induced | |
| Isoform | 1 isoform(s) |
Section 1
Real Curated SP5 Western Blot Protocols
Literature-validated Western blot parameters for SP5 — gel percentage, transfer, blocking, antibody incubation and detection, extracted from published methods.
| Sample / lysate | MCF-7 at 40ug. After electrophoresis, proteins were transferred to a nitrocellulose membrane at 150 mA for 50-90 minutes. Blocked the membrane with 5% non-fat milk/TBS for 1.5 hour at RT. The membrane was incubated with rabbit anti-SP5 antigen affinity purified polyclonal antibody (Catalog # PB9443) at 0.5 μg/mL overnight at 4°C, then washed with TBS-0.1%Tween 3 times with 5 minutes each and probed with a goat anti-rabbit IgG-HRP secondary antibody at a dilution of 1:5000 for 1.5 hour at RT. The signal is developed using an Enhanced Chemiluminescent detection (ECL) kit (Catalog # EK1002) with Tanon 5200 system. A specific band was detected for SP5 at approximately 42 kDa. The expected band size for SP5 is at 42 kDa |
| Gel % | 10–12% |
| Transfer | nitrocellulose membrane, 150 mA, 50–90 min |
| Membrane | nitrocellulose |
| Blocking | 5% non-fat milk / TBS, 1.5 h RT |
| Primary antibody | 0.5 µg/mL |
| Primary incubation | overnight at 4 °C |
| Secondary antibody | goat anti-rabbit IgG-HRP, 1:5000 |
| Wash | TBS-0.1% Tween, 3 × 5 min |
| Detection | ECL |
| Exposure / imaging | Tanon 5200 |
| Observed band | 42 kDa |
Section 2
What Is the Expected SP5 Western Blot Band Size?
SP5 has a 42 kDa predicted mass and runs at the same ~42 kDa on blots, since it lacks glycosylation, disulfide dimerization, and alternative splicing.
| single sharp band at ~42 kDa | matches the predicted mass, with no glycosylation, cleavage, or dimerization annotated to shift SP5's apparent size |
| no smear or diffuse band above 42 kDa | SP5 has no annotated glycosylation sites, so there is no glycoform-driven heterogeneity to broaden the band |
| no band near ~84 kDa | no disulfide bonds are annotated for SP5, so it does not form a disulfide-linked dimer even under partial reduction |
| single band, no doublet or extra bands | only one isoform is annotated for SP5, so no splice-variant doublet is expected |
| stronger signal in nuclear-enriched fractions than in whole-cell lysate | SP5 is a nuclear-localized transcription factor, so nuclear lysis/extraction improves detection relative to standard whole-cell lysate |
💡Expected SP5 appearanceExpect a single, sharp band at approximately 42 kDa, consistent with both the predicted mass and the empirically observed band, since SP5 has no glycosylation, disulfide-linked dimerization, or alternative splicing to shift its migration.
| Predicted mass from UniProt (42 kDa, 398 aa) | sets the expected migration position; the observed band matches closely at ~42 kDa |
| Absence of glycosylation sites | prevents any upward smear or shift from heterogeneous glycoforms, keeping the band sharp near predicted size |
| Absence of disulfide bonds/oligomerization | no higher-molecular-weight dimer band appears under non-reducing or partially reducing conditions |
| Single annotated isoform | no doublet or extra bands from alternative splice variants |
| No signal peptide or propeptide | no proteolytic maturation step, so there is no smaller cleaved band relative to the full-length protein |
| Nuclear subcellular localization | detection is stronger with nuclear or nuclear-enriched lysis buffers; cytoplasmic-only fractionation can under-represent the signal |
| Situation | Likely cause | Next action |
|---|---|---|
| No band in lysate | SP5 is a nuclear transcription factor and may be under-extracted with standard whole-cell lysis or absent in cell types with low SP5 expression | use a nuclear-enriched lysis buffer, confirm the cell line expresses SP5, and include a known-positive nuclear lysate as control |
| Weak or no signal | transcription factors like SP5 are typically low-abundance nuclear proteins | increase total protein loaded, enrich for nuclear fraction, and optimize antibody concentration and incubation time |
| Band higher than expected | incomplete denaturation or nonspecific aggregation, since SP5 has no annotated disulfide bonds to justify a true dimer band | ensure samples are fully heated and reduced before loading and check for aggregation artifacts |
| Band lower than expected | proteolytic degradation during lysate preparation, since no propeptide cleavage exists to explain a smaller native fragment | prepare lysates fresh on ice with protease inhibitors and minimize freeze-thaw cycles |
| Multiple bands | nonspecific antibody binding or degradation products, since only a single isoform is annotated for SP5 | validate antibody specificity with a knockdown/knockout or overexpression control |
Experiment evidence
Western blot images showing SP5 band
PB9443 · SP5
← swipe / scroll for more images →
Real WB data behind the band-size expectations in this section.
Sample controls for SP5 Western blot
🧪For positive controls for SP5 in Western blot, you can use lysate from cells transiently transfected to overexpress SP5, since the Human Protein Atlas reports no confirmed positive tissues or cell lines for this transcription factor.
Positive control: SP5-transfected cell lysate
Negative control: ubiquitously expressed; use siRNA knockdown or KO line
Loading controls: Run GAPDH and β-actin antibodies alongside a total-protein stain (e.g., stain-free gel, Ponceau S, or REVERT) as loading controls.
⚠️Feasibility: As a low-abundance nuclear transcription factor lacking HPA expression data, a clean endogenous positive tissue cannot be confirmed, so specificity should be validated with overexpression lysate paired with siRNA knockdown or a knockout line as the negative control.
Comprehensive Human Protein Atlas IHC scoring per tissue. Rows are taken directly from the HPA tissue chart — click any row's HPA link to view the source.
Positive expression · recommended positive controls
| Tissue | Cell type | Level | Evidence | Source |
|---|
Undetected expression · recommended negative controls
| Tissue | Cell type | Level | Evidence | Source |
|---|
Section 3
Advanced SP5 Western Blot Tips
Deeper troubleshooting and optimisation questions for SP5, answered from its protein features.
Does SP5 run at its predicted 42 kDa on blots?
SP5 has no signal peptide, propeptide, glycosylation, or disulfide bonds reported, so no major post-translational mass shift is expected; the observed band at ~42 kDa matches the predicted mass of 42 kDa. As a nuclear zinc-finger transcription factor, minor migration differences of a few kDa are normal and don't indicate isoform or PTM effects; treat larger shifts as validation-worthy.
How do I induce SP5 expression for Western blot?
SP5 acts as a transcriptional effector of canonical Wnt/β-catenin signaling, so expression can be upregulated by activating Wnt signaling, for example with Wnt3a-conditioned medium or the GSK3 inhibitor CHIR99021, in Wnt-responsive cell lines. Always run an untreated parallel lane alongside the treated lane to confirm induction rather than assuming baseline expression.
How should I optimize blocking for SP5 detection?
Test the primary antibody at three serial dilutions (e.g., 1:500, 1:1000, 1:2000) on a positive control lysate to find the best signal-to-background ratio, since no unusual PTMs or glycosylation on SP5 complicate blocking. Standard 5% non-fat milk or BSA blocking is typically sufficient for this nuclear zinc-finger transcription factor.
What transfer method to use for SP5 Western blot?
At ~42 kDa, standard wet or semi-dry transfer onto PVDF or nitrocellulose membranes works well; no special low-molecular-weight or high-molecular-weight transfer adjustments are needed for this nuclear DNA-binding zinc-finger protein. Standard transfer times (60-90 minutes wet, or manufacturer-recommended semi-dry protocols) are sufficient for efficient transfer of a mid-size nuclear factor.
How should I quantitate SP5 band intensity accurately?
Because SP5 is a nuclear transcription factor, normalize signal to a nuclear loading control such as Lamin B1 or Histone H3 rather than a cytoplasmic housekeeping protein, since total-protein normalization can misrepresent nuclear-enriched targets. Use a linear-range exposure and quantify with densitometry software to avoid signal saturation, since SP5 is typically expressed at moderate to low endogenous levels.
What causes unexpected bands when detecting SP5?
Since SP5 has a single reported isoform and no known glycosylation or disulfide-linked oligomerization, extra bands most likely reflect antibody cross-reactivity, degradation of this nuclear zinc-finger protein during lysis, or nonspecific binding rather than genuine isoforms. Confirm specificity with a positive control lysate and, if available, an SP5 knockdown or knockout sample.
Boster reagents
Best SP5 Western Blot Antibodies
BosterBio's SP5 antibodies are among the best-performing WB antibodies on the market — well cited, thoroughly validated, and orthogonally cross-validated against negative tissues and complementary methods.
Real WB data
Anti-Sp5 Antibody Picoband®
Cat # PB9443
Our recommended anti-SP5 Western blot antibodies are top-performing, extensively cited, and rigorously validated, with orthogonal confirmation against negative tissue and complementary detection methods to ensure specific, reproducible results you can trust.
Which to pick: Only one Boster anti-SP5 antibody is catalogued, PB9443, which includes a genuine Western blot image showing detection in MCF-7 whole cell lysate, making it the clear, straightforward choice for your SP5 Western blot.
Source: BosterBio SP5 gene-info card — filtered to Western-blot-capable antibodies; each card shows that product's actual WB validation figure.
References
- UniProt Consortium. UniProt entry Q6BEB4.
- Human Protein Atlas. SP5 tissue expression.