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SENSITIVITY MW (kDa)
Transfected Only
Image

Immunoprecipitation of COS-7 cells transfected with a construct expressing HA-tagged Akt using Rabbit (DA1E) mAb IgG XP® Isotype Control (Magnetic Bead Conjugate) #8726 (Lane 2) or HA-Tag (C29F4) Rabbit mAb (Magnetic Bead Conjugate) (Lane 3). Lane 1 is 10% lysate. The western blot was probed using HA-Tag (6E2) Mouse mAb (HRP Conjugate) #2999.

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Immunoprecipitation for Analysis by Western Blotting

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 equivalently purified water.

  1. 20X Phosphate Buffered Saline (PBS): (#9808).
  2. 10X Cell Lysis Buffer: (#9803) 20 mM Tris (pH 7.5), 150 mM NaCl, 1 mM EDTA, 1 mM EGTA, 1% Triton X-100, 2.5 mM Sodium pyrophosphate, 1 mM β-glycerophosphate, 1 mM Na3VO4, 1 μg/ml Leupeptin

    NOTE: CST recommends adding 1 mM PMSF (#8553) before use*.

  1. 3X SDS Sample Buffer: (#7722) 187.5 mM Tris-HCl (pH 6.8 at 25°C), 6% w/v SDS, 30% glycerol, 150 mM DTT, 0.03% w/v bromophenol blue
  2. 6-Tube Magnetic Separation Rack: (#7017).
  3. 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.
  4. 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 PBS.
  3. Remove PBS and add 0.5 ml 1X ice-cold cell lysis buffer to each plate (10 cm) and incubate the plates on ice for 5 minutes.
  4. Scrape cells off the plates and transfer to microcentrifuge tubes. Keep on ice.
  5. Sonicate samples on ice three times for 5 seconds each.
  6. Microcentrifuge for 10 minutes at 4°C, 14,000 x g, and transfer the supernatant to a new tube. If necessary, lysate can be stored at –80°C.

C. Immunoprecipitation

  1. Take 200 μl cell lysate and add 20 µl of the immobilized antibody, incubate with rotation overnight at 4°C.
  2. Microcentrifuge for 30 seconds at 4°C. Wash pellet five times with 500 µl of 1X cell lysis buffer. Keep on ice during washes.
  3. Proceed to sample analysis by western blotting 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. Pellet magnetic beads by placing the tubes in a magnetic separation rack (#7017) and wait 1 to 2 min for solution to clear. Wash pellet five times with 500 µl of 1X cell lysis buffer. Kepp on ice during washes.
  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 2007

protocol id: 408

Product Usage Information

Application Dilutions
Immunoprecipitation 1:20

Storage: Supplied in PBS Buffer (pH 7.2), 0.1% Tween® 20. Store at 4°C. Do not aliquot the antibodies.

Specificity / Sensitivity

HA-Tag (C29F4) Rabbit mAb (Magnetic Bead Conjugate) detects exogenously expressed proteins containing the HA epitope tag.


Species Reactivity: All Species Expected

Source / Purification

Monoclonal antibody is produced by immunizing animals with a synthetic peptide containing the influenza hemagglutinin epitope (YPYDVPDYA).

Epitope tags are useful for the labeling and detection of proteins using immunoblotting, immunoprecipitation, and immunostaining techniques. Because of their small size, they are unlikely to affect the tagged protein's biochemical properties.


The HA tag is derived from an epitope of the influenza hemagglutinin protein which has been used extensively as a general epitope tag in expression vectors (1).


1.  Field, J. et al. (1988) Mol Cell Biol 8, 2159-65.



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XP® is a trademark of Cell Signaling Technology, Inc.
U.S. Patent No. 5,675,063.