RhoA Pull-down Activation Assay Biochem Kit (bead pull-down format) - 80 Assays

RhoA Activation Assay Biochem Kit (bead pull-down format) - 80 Assays

Product Uses Include

Analysis of in vivo RhoA activation


The Rho switch operates by alternating between an active, GTP-bound state and an inactive, GDP-bound state.  Understanding the mechanisms that regulate activation / inactivation of the GTPases is of obvious biological significance and is a subject of intense investigation.  The fact that many Rho family effector proteins will specifically recognize the GTP bound form of the protein has been exploited experimentally to develop a powerful affinity purification assay that monitors RhoA protein activation.  The assay uses the Rho binding domain (RBD) of the Rho effector protein, Rhotekin.  The RBD motif has been shown to bind specifically to the GTP-bound form of RhoA. The fact that the RBD region of Rhotekin has a high affinity for GTP-RhoA and that Rhotekin binding results in a significantly reduced intrinsic and catalytic rate of GTP hydrolysis make it an ideal tool for affinity purification of GTP-RhoA from cell lysates.  The Rhotekin-RBD protein supplied in this kit contains Rhotekin residues 7-89 and is in the form of a GST fusion protein, which allows one to "pull-down" the Rhotekin-RBD/Rho-GTP complex with brightly colored glutathione affinity beads. The assay therefore provides a simple means of quantitating RhoA activation in cells. The amount of activated RhoA is determined by a western blot using a RhoA specific antibody.

Kit contents
The kit contains sufficient materials for 80 assays depending on activation levels of Rho in cells and includes reagents for positive and negative controls. The following components are included:

  1. GST-tagged Rhotekin-RBD protein on colored agarose beads (Cat. # RT02)
  2. RhoA-specific monoclonal antibody (Cat. # ARH03)
  3. His-tagged RhoA protein (Cat. # RH01)
  4. GTPγS: (non-hydrolyzable GTP analog) (Cat. # BS01)
  5. GDP
  6. Cell lysis Buffer
  7. Wash Buffer
  8. Loading Buffer
  9. STOP Buffer
  10. Protease inhibitor cocktail (Cat. # PIC02)
  11. Manual with detailed protocols and extensive troubleshooting guide

Figure 1. The brightly colored glutathione agarose beads in BK036 makes the kit easy to use.

Equipment needed

  1. SDS-PAGE minigel system and western blotting transfer apparatus

Example results
The RhoA activation assay was tested by loading the RhoA protein in cell lysates with either GTPγS or GDP. As expected, the GTPγS-loaded RhoA is very efficiently precipitated while very little GDP-loaded RhoA is precipitated (Fig. 2).


Figure 2. Results from BK036 RhoA activation assay. Activated Rho was precipitated and detected in a Western blot using kit BK036. The first lane shows a 50 ng recombinant His-tagged RhoA standard (Rec. His-RhoA). The following lanes shows the pull-down of inactive, GDP-loaded RhoA (RhoA-GDP PD) or active, GTPγS-loaded RhoA (RhoA-GTP PD) from equal amounts of cell lysates.

Please check out the new version of the Rac Activation Assay and associated products:

G-LISA Products:
Cdc42 G-LISA™ Activation Assay, colorimetric format (Cat.# BK127)
Rac1 G-LISA™ Activation Assay, luminescence format (Cat.# BK126)
Rac1,2,3 G-LISA™ Activation Assay, colorimetric format (Cat.# BK125)
RhoA G-LISA™ Activation Assay, colorimetric format (Cat.# BK124)
RhoA G-LISA™ Activation Assay, luminescence format (Cat.# BK121)

Associated Products:
Anti-Cdc42 monoclonal antibody (Cat.# ACD03)
Anti-Rac1 monoclonal antibody (Cat.# ARC03)
Anti-RhoA monoclonal antibody (Cat.# ARH03)

For product Datasheets and MSDSs please click on the PDF links below.   For additional information, click on the FAQs tab above or contact our Technical Support department at tservice@cytoskeleton.com

Lee, J., Choi, J.A., Ju, Hh. et al. Role of MCP-1 and IL-8 in viral anterior uveitis, and contractility and fibrogenic activity of trabecular meshwork cells. Sci Rep 11, 14950 (2021). https://doi.org/10.1038/s41598-021-94391-2 (2021)

Rolle, IG. Et. Al, Heart failure impairs the mechanotransduction properties of human cardiac pericytes https://doi.org/10.1016/j.yjmcc.2020.10.016 (2021)

Iweka, A. et al. The lipid phosphatase‐like protein PLPPR1 associates with RhoGDI1 to modulate RhoA activation in response to axon growth inhibitory molecules. J. Neurochem. jnc.15271 (2021) doi:10.1111/jnc.15271.

Zhou, Y. et al. Upregulation of ARHGAP30 attenuates pancreatic cancer progression by inactivating the β-catenin pathway. Cancer Cell Int. 20, 1–12 (2020).

Ramírez‐Ramírez, D. et al. Rac1 is necessary for capacitation and acrosome reaction in guinea pig spermatozoa. J. Cell. Biochem. 121, 2864–2876 (2020).

Guo, Y. et al. Cytotoxic necrotizing factor 1 promotes bladder cancer angiogenesis through activating RhoC. FASEB J. 34, 7927–7940 (2020).

Wang, R. et al. Rac1 silencing, NSC23766 and EHT1864 reduce growth and actin organization of bladder smooth muscle cells. Life Sci. 261, 118468 (2020).

Wee, K. et al. Snail induces epithelial cell extrusion by regulating RhoA contractile signalling and cell–matrix adhesion. J. Cell Sci. 133, (2020).

Barabutis, N. et al. Protective mechanism of the selective vasopressin V1A receptor agonist selepressin against endothelial barrier dysfunction. J. Pharmacol. Exp. Ther. 375, 286–295 (2020).

Wang, Q. et al. Thymol alleviates AGEs-induced podocyte injury by a pleiotropic effect via NF-κB-mediated by RhoA/ROCK signalling pathway. Cell Adh. Migr. 14, 42–56 (2020).

Kitchen, G. B. et al. The clock gene Bmal1 inhibits macrophage motility, phagocytosis, and impairs defense against pneumonia. Proc. Natl. Acad. Sci. U. S. A. 117, 1543–1551 (2020).

Tang, Jingshu et al. TIMP1 preserves the blood-brain barrier through interacting with CD63/integrin β 1 complex and regulating downstream FAK/RhoA signaling. Acta pharmaceutica Sinica. B vol. 10,6 (2020): 987-1003. doi:10.1016/j.apsb.2020.02.015
Moodley, Serisha et al. RET isoform-specific interaction with scaffold protein Ezrin promotes cell migration and chemotaxis in lung adenocarcinoma. Lung cancer (Amsterdam, Netherlands) vol. 142 (2020): 123-131. doi:10.1016/j.lungcan.2020.02.004

C. Yan et al., 2014. Discovery and characterization of small molecules that target the GTPase Ral. Nature. doi: 10.1038/nature13713.

Xie et al., 2013. Activation of RhoA/ROCK regulates NF-κB signaling pathway in experimental diabetic nephropathy. Mol. Cell. Endocrinol.  369, 86-97.

Zhan et al., 2013. The effect of an NgR1 antagonist on the neuroprotection of cortical axons after cortical infarction in rats. Neurochem. Res. doi: 10.1007/s11064-013-1026-z.

Tong et al., 2013. Activation of RhoA in alcohol-induced intestinal barrier dysfunction. Inflammation. doi: 10.1007/s10753-013-9601-7.

Cheng et al., 2012. Infrasonic noise induces axonal degeneration of cultured neurons via a Ca2+ influx pathway. Toxicol. Lett. v 212, pp 190-197.

Lee et al., 2012. Barrier protective effects of withaferin A in HMGB1-induced inflammatory responses in both cellular and animal models. Toxicol. Appl. Pharmacol. v 262, pp 91-98.

Antonyak et al., 2012. RhoA triggers a specific signaling pathway that generates transforming microvesicles in cancer cells. Oncogene. doi:10.1038/onc.2011.636.

Nithipatikom et al., 2012. Cannabinoid receptor type 1 (CB1) activation inhibits small GTPase RhoA activity and regulates motility of prostate carcinoma cells. Endocrinology. v 153, pp 29-41.

Droppelmann et al., 2012. Rho guanine nucleotide exchange factor is an NFL mRNA destabilizing factor that forms cytoplasmic inclusions in amyotrophic lateral sclerosis. Neurobiol. Aging. http://dx.doi.org/10.1016/j.neurobiolaging.2012.06.021.

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Khan et al., 2011. Geranylgeranyltransferase type I (GGTase-I) deficiency hyperactivates macrophages and induces erosive arthritis in mice. J. Clin. Invest. doi:10.1172/JCI43758.

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Question 1: I have high background and/or multiple bands on my western blot.  How can I fix this?

Answer 1:  There are multiple causes of high background and/or multiple bands.  Some suggestions to improve background signal include:

  1.   When blotting use 70v for 45min only as the small G-proteins are very mobile.
  2. Fully remove SDS from the gel by using a non-SDS containing buffer for transfer and performing a full 15 min gel wash step in the transfer buffer before blotting.
  3. Dry the PVDF membrane for 30 min after transfer and before blocking (not necessary for nitrocellulose)
  4. Making sure that the TBST contains 10 mM Tris, 0.05% Tween 20 and 150 mM NaCl.
  5. Incubating with the primary antibody overnight at 4°C and using the appropriate ECL detection system. 


Question 2: How much of the beads should I use for my pull-down experiments?

Answer 2:  Rhotekin-RBD beads (Cat. # RT02) will bind to Rho-GDP with a much lower affinity than Rho-GTP.  If too many rhotekin-RBD beads are added to the pull-down assay there will be significant binding to inactive (GDP-bound) RhoA.  The result of this will be an underestimation of RhoA activation.  For this reason, we highly recommend performing a bead titration to determine optimal conditions for any given RhoA activation or inactivation assay.  Once optimal conditions have been established, bead titrations should no longer be necessary. We recommend 25, 50 and 100 μg bead titrations.


Question 3:  How can I test whether the beads are working properly?

Answer 3:  A standard biological assay for rhotekin-RBD beads consists of a RhoA protein pull-down from cells loaded with either GTPγS (Cat. # BS01) or GDP.  Here are guidelines to follow (see Cat. # RT02 and BK036 datasheets for more details):


Positive Cellular Protein Control:

Total cell lysate (300 – 800 μg) should be loaded with GTPγS as a positive control for the pull-down assay.  The following reaction details how to load endogenous RhoA with the nonhydrolysable GTP analog (GTPγS).  This is an excellent substrate for rhotekin-RBD beads and should result in a strong positive signal in a pull-down assay.


a) Perform GTP loading on 300 – 800 μg of cell lysate (0.5 mg/ml protein concentration) by adding 1/10th volume of Loading Buffer.

b) Immediately add 1/100th volume of GTPγS (200 μM final concentration).  Under these conditions, 5 - 10% of the RhoA protein will load with non-hydrolysable GTPγS and will be “pulled-down” with the rhotekin-RBD beads in the assay.

c) Incubate the control sample at 30°C for 15 min with gentle rotation.

d) Stop the reaction by transferring the tube to 4°C and adding 1/10th volume of STOP Buffer.

e) Use this sample immediately in a pull-down assay.


Negative Cellular Protein Control:

This reaction should be performed in an identical manner to the Positive Control reaction except that 1/100th volume of GDP (1 mM final concentration) should be added to the reaction in place of the GTPγS.  Loading endogenous RhoA with GDP will inactivate RhoA and this complex will bind very poorly to rhotekin-RBD beads.



If you have any questions concerning this product, please contact our Technical Service department at tservice@cytoskeleton.com