Recombinant Human GRK4 Protein: Function & Research Use

Recombinant Human GRK4 Protein is a eukaryotically expressed serine/threonine kinase that phosphorylates activated G protein-coupled receptors, making it an essential tool for investigating GPCR desensitization, dopamine receptor biology, and the molecular mechanisms underlying hypertension.

Protein Name

Recombinant Human GRK4 Protein

Also Known As

G Protein-Coupled Receptor Kinase 4; GPRK4; GRK4

Protein Class

Serine/Threonine Kinase (AGC kinase family)

Species

Human (Homo sapiens)

Primary Function

Phosphorylation and desensitization of activated GPCRs, including dopamine receptors D1 and D3

Key Research Area

Hypertension, GPCR signaling, renal sodium transport regulation

SKU

rp372285

Biological Background of GRK4

G protein-coupled receptor kinase 4 (GRK4) is a member of the GRK subfamily of serine/threonine kinases within the broader AGC kinase superfamily. GRK4 belongs to the GRK1 subfamily alongside GRK1 and GRK7, and it is distinguished from other GRK family members by its constitutive membrane association and a high degree of autophosphorylation activity.

GRK4 is expressed predominantly in the testes and, at lower levels, in the kidney and brain. Its primary molecular role is the phosphorylation of agonist-occupied, activated GPCRs at intracellular serine and threonine residues. This phosphorylation event recruits arrestin proteins, sterically uncoupling the receptor from its cognate G protein and initiating receptor internalization — the hallmark process of homologous GPCR desensitization.

In the kidney, GRK4 phosphorylates the dopamine D1 receptor (DRD1) and D3 receptor (DRD3), impairing dopamine-mediated inhibition of sodium reabsorption. Gain-of-function variants of GRK4 have been associated with essential hypertension in human genetic studies, making this kinase a clinically relevant target for cardiovascular research.

Biochemical Properties and Product Specifications

The Recombinant Human GRK4 Protein (SKU: rp372285) is produced to support biochemical and cell-based assay workflows. As a recombinant protein, it retains the catalytic kinase domain responsible for substrate phosphorylation, enabling its use in in vitro kinase activity assays.

Key biochemical attributes of GRK4 include:

• Enzyme class: Serine/threonine-protein kinase
• Catalytic activity: ATP + [GPCR] → ADP + phospho-[GPCR]
• Autophosphorylation: GRK4 undergoes constitutive autophosphorylation, which modulates its basal activity
• Membrane association: The native protein associates with the plasma membrane; the recombinant form is suitable for solution-phase assays

Note: Specific purity grade, molecular weight, tag information, formulation buffer, and storage conditions should be confirmed against the current product datasheet (absea#PP-6334). Researchers are advised to consult the Certificate of Analysis for lot-specific data.

Research Applications

Recombinant Human GRK4 Protein is a versatile reagent applicable across multiple research domains:

• In vitro kinase assays: Used to assess phosphorylation of GPCR-derived peptide substrates or full-length receptor preparations, enabling profiling of GRK4 inhibitors and activators.
• Drug discovery and inhibitor screening: GRK4 is an emerging target for antihypertensive drug development; the recombinant protein supports high-throughput screening and selectivity profiling against other GRK isoforms.
• Protein–protein interaction studies: GRK4 interacts with multiple partners including arrestins and calmodulin; the recombinant protein can be used in pull-down, co-immunoprecipitation, and surface plasmon resonance experiments.
• Structural biology: Suitable as an antigen for antibody production and validation, or as a reference standard in Western blot and ELISA workflows.
• Hypertension mechanistic research: Enables investigation of how GRK4 gain-of-function variants alter dopamine receptor phosphorylation and renal sodium handling.

Handling, Storage, and Quality Considerations

To maintain the activity and integrity of Recombinant Human GRK4 Protein, researchers should observe the following general best practices for recombinant kinase proteins:

• Storage: Store at –80 °C for long-term preservation. Avoid repeated freeze–thaw cycles, which can reduce enzymatic activity. Aliquot upon receipt where feasible.
• Reconstitution: If supplied lyophilized, reconstitute in the buffer specified in the product datasheet. Allow the vial to equilibrate to room temperature before opening.
• Working concentration: Optimize empirically for each assay format; consult the datasheet for recommended starting concentrations.
• Carrier protein: Addition of BSA (0.1–0.5%) to dilution buffers may stabilize the protein during extended assay workflows.
• Quality control: Each lot undergoes QC testing; refer to the Certificate of Analysis for purity (SDS-PAGE), activity data, and endotoxin levels where applicable.

Specific buffer composition, concentration, and activity unit definitions are provided on the product-specific datasheet (absea#PP-6334). Always consult the most current version before use.

Frequently asked questions

What is GRK4 and why is it important in cardiovascular research?

GRK4 (G protein-coupled receptor kinase 4) is a serine/threonine kinase that phosphorylates activated GPCRs to initiate receptor desensitization. In the kidney, GRK4 phosphorylates dopamine receptors D1 and D3, impairing their ability to inhibit sodium reabsorption. Gain-of-function variants of GRK4 have been associated with essential hypertension in human genetic studies, making it a key research target for understanding blood pressure regulation.

What research applications is Recombinant Human GRK4 Protein suitable for?

Recombinant Human GRK4 Protein is suitable for in vitro kinase activity assays, inhibitor screening and drug discovery, protein–protein interaction studies (e.g., pull-down and co-IP), antibody production and validation, and Western blot reference standards. It is particularly valuable for researchers studying GPCR desensitization pathways and the molecular basis of hypertension.

How should Recombinant Human GRK4 Protein be stored to maintain activity?

For long-term storage, keep the protein at –80 °C and avoid repeated freeze–thaw cycles by preparing single-use aliquots upon receipt. If the protein is supplied lyophilized, reconstitute it in the buffer specified in the product datasheet and allow the vial to reach room temperature before opening. Refer to the Certificate of Analysis and product datasheet (absea#PP-6334) for lot-specific storage instructions.

How does GRK4 differ from other members of the GRK family?

GRK4 is unique among GRK family members in that it undergoes constitutive autophosphorylation and is constitutively associated with the plasma membrane independently of receptor activation. Unlike GRK2 and GRK3, which are cytosolic and translocate to the membrane upon GPCR activation, GRK4 is largely confined to testis and kidney. Its restricted tissue expression and constitutive membrane localization distinguish it functionally from the ubiquitously expressed GRK2 and GRK5.

References

1. Premont RT, Gainetdinov RR. Physiological roles of G protein-coupled receptor kinases and arrestins. Annual Review of Physiology. 2007;69:511-534. doi:10.1146/annurev.physiol.69.022405.154731
2. Felder RA, Jose PA. Mechanisms of disease: the role of GRK4 in the etiology of essential hypertension and salt sensitivity. Nature Clinical Practice Nephrology. 2006;2(11):637-650. doi:10.1038/ncpneph0301
3. Penela P, Murga C, Ribas C, Lafarga V, Mayor F Jr. The complex G protein-coupled receptor kinase 2 (GRK2) interactome unveils new physiopathological targets. British Journal of Pharmacology. 2010;160(4):821-832. doi:10.1111/j.1476-5381.2010.00727.x

Products are supplied for research and development use only. Not for use in humans, animals, diagnosis, or therapy.