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REACTIVITY SENSITIVITY MW (kDa)
M Endogenous 40
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Immunoprecipitation and western blot analysis of extracts from mouse brain. Lane 1 contains lysate input, lane 2 was immunoprecipitated with Gα(o) Antibody (IP Preferred) and lane 3 was immunoprecipitated with non-specific rabbit IgG. Western blot analysis was performed using Gα(o) Antibody #3975.

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Immunoprecipitation for Native Proteins

This protocol is intended for immunoprecipitation of native proteins for analysis by western immunoblot or kinase activity.

A. Solutions and Reagents

NOTE: Prepare solutions with reverse osmosis deionized (RODI) or equivalent grade water.

  1. 20X Phosphate Buffered Saline (PBS): (#9808) To prepare 1 L of 1X PBS, add 50 ml 20X PBS to 950 ml dH2O, mix.
  2. 10X Cell Lysis Buffer: (#9803) To prepare 10 ml of 1X cell lysis buffer, add 1 ml cell lysis buffer to 9 ml dH2O, mix.

    NOTE: Add 1 mM PMSF (#8553) immediately prior to use.

  3. 3X SDS Sample Buffer: Blue Loading Pack (#7722) or Red Loading Pack (#7723) Prepare fresh 3X reducing loading buffer by adding 1/10 volume 30X DTT to 1 volume of 3X SDS loading buffer.
  4. Protein A Magnetic Beads: Use Protein A (#8687) for rabbit IgG immunoprecipitation.
  5. 6-Tube Magnetic Separation Rack: (#7017).
  6. 10X Kinase Buffer (for kinase assays): (#9802) To Prepare 1 ml of 1X kinase buffer, add 100 µl 10X kinase buffer to 900 µl dH2O, mix.
  7. ATP (10 mM) (for kinase assays): (#9804) To prepare 0.5 ml of ATP (200 µM), add 10 µl ATP (10 mM) to 490 µl 1X kinase buffer.

B. Preparing Cell Lysates

  1. Aspirate media. Treat cells by adding fresh media containing regulator for desired time.
  2. To harvest cells under nondenaturing conditions, remove media and rinse cells once with ice-cold 1X PBS.
  3. Remove PBS and add 0.5 ml ice-cold 1X cell lysis buffer to each plate (10 cm) and incubate on ice for 5 min.
  4. Scrape cells off the plate and transfer to microcentrifuge tubes. Keep on ice.
  5. Sonicate on ice three times for 5 sec each.
  6. Microcentrifuge for 10 min at 4°C, 14,000 x g and transfer the supernatant to a new tube. The supernatant is the cell lysate. If necessary, lysate can be stored at -80°C.

C. Immunoprecipitation

Cell Lysate Pre-Clearing (Optional)

  1. Vortex to mix beads.
  2. Add 10–30 µl of 50% Protein A magnetic bead slurry of to 200 µl cell lysate at 1 mg/ml.
  3. Incubate with rotation at 4°C for 30–60 min.
  4. Pellet beads using magnetic separation rack. Transfer the supernatant to a fresh tube.
  5. Proceed to immunoprecipitation below.

Immunoprecipitation

  1. Add primary antibody (at the appropriate dilution as recommended in the product datasheet) to 200 µl cell lysate at 1 mg/ml. Incubate with rotation overnight at 4°C.
  2. Add protein A magnetic beads (10–30 µl of 50% bead slurry). Incubate with rotation for 10–30 min at 4°C.
  3. Pellet beads using magnetic separation rack. Wash pellet five times with 500 µl of 1X cell lysis buffer. Keep on ice between washes.
  4. Proceed to analyze by western immunoblotting or kinase activity (section D).

D. Sample Analysis

Proceed to one of the following specific set of steps.

For Analysis by Western Immunoblotting

  1. Resuspend the pellet with 20 µl 3X SDS sample buffer. Vortex, then microcentrifuge for 30 sec at 14,000 x g.
  2. Heat the sample to 95–100°C for 2-5 min and microcentrifuge for 1 min at 14,000 x g.
  3. Load the sample (15–30 µl) on a 4–20% gel for SDS-PAGE.
  4. Analyze sample by western blot (see Western Immunoblotting Protocol).

NOTE: To minimize masking caused by denatured IgG heavy chains (~50 kDa), we recommend using Mouse Anti-Rabbit IgG (Light-Chain Specific) (L57A3) mAb (#3677) or Mouse Anti-Rabbit IgG (Conformation Specific) (L27A9) mAb (#3678) (or HRP conjugate #5127). To minimize masking caused by denatured IgG light chains (~25 kDa), we recommend using Mouse Anti-Rabbit IgG (Conformation Specific) (L27A9) mAb (#3678) (or HRP conjugate #5127).

For Analysis by Kinase Assay

  1. Wash pellet twice with 500 µl 1X kinase buffer. Keep on ice.
  2. Suspend pellet in 40 µl 1X kinase buffer supplemented with 200 µM ATP and appropriate substrate.
  3. Incubate for 30 min at 30°C.
  4. Terminate reaction with 20 µl 3X SDS sample buffer. Vortex, then microcentrifuge for 30 sec.
  5. Transfer supernatant containing phosphorylated substrate to another tube.
  6. Heat the sample to 95–100°C for 2–5 min and microcentrifuge for 1 min at 14,000 x g.
  7. Load the sample (15–30 µl) on SDS-PAGE (4–20%).

posted December 2008

revised November 2013

protocol id: 410

Product Usage Information

Application Dilutions
Immunoprecipitation 1:50

Storage: Supplied in 10 mM sodium HEPES (pH 7.5), 150 mM NaCl, 100 µg/ml BSA and 50% glycerol. Store at –20°C. Do not aliquot the antibody.

Specificity / Sensitivity

Gα(o) Antibody (IP Preferred) detects endogenous levels of total Gα(o) protein and is recommended for immunoprecipitation.


Species Reactivity: Mouse
Species predicted to react based on 100% sequence homology: Human, Rat

Source / Purification

Polyclonal antibodies are produced by immunizing animals with a synthetic peptide corresponding to residues surrounding Arg15 of human Gα(o). Antibodies are purified by protein A and peptide affinity chromatography.

Heterotrimeric guanine nucleotide-binding proteins (G proteins) consist of α, β and γ subunits and mediate the effects of hormones, neurotransmitters, chemokines and sensory stimuli. To date, over 20 known Gα subunits have been classified into four families, Gα(s), Gα(i/o), Gα(q) and Gα(12), based on structural and functional similarities (1,2). Phosphorylation of Tyr356 of Gα(q)/Gα(11) is essential for activation of the G protein, since phenylalanine substitution for Tyr356 changes the interaction of Gα with receptors and abolishes ligand-induced IP3 formation (3).


Gα(o) is the most abundant G protein in the brain and couples to serotonin, dopamine, GABA (B), opioid, glutamate and cholinergic receptors (4). Gα(o) -/- mice have neurological defects such as tremors, seizures and poor motor coordination (5).


1.  Offermanns, S. (2001) Oncogene 20, 1635-42.

2.  Pierce, K.L. et al. (2002) Nat Rev Mol Cell Biol 3, 639-50.

3.  Umemori, H. et al. (1997) Science 276, 1878-81.

4.  Jiang, M. and Bajpayee, N.S. (2009) Neurosignals 17, 23-41.

5.  Jiang, M. et al. (1998) Proc Natl Acad Sci USA 95, 3269-74.


Entrez-Gene Id 2775
Swiss-Prot Acc. P09471


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