What Is GPSM1 and Why Does It Matter?

G-Protein Signaling Modulator 1 (GPSM1), also referred to as AGS3 (Activator of G-protein Signaling 3) or LGN, is a multifunctional scaffold protein that plays a central role in heterotrimeric G-protein signal transduction. The protein is characterized by two principal structural domains: an N-terminal tetratricopeptide repeat (TPR) domain, which mediates interactions with partner proteins such as NuMA and mInsc, and a C-terminal region containing multiple GoLoco (or GPR) motifs that bind selectively to Gα subunits in their GDP-bound (inactive) state.

By acting as a guanine nucleotide dissociation inhibitor (GDI) for Gαi/o subunits, GPSM1 stabilizes the inactive GDP-bound conformation of Gα, effectively modulating the duration and amplitude of G-protein-mediated downstream signaling. Beyond classical GPCR signaling, GPSM1 has emerged as a critical determinant of cell polarity and asymmetric cell division, processes that are fundamental to tissue development, stem cell fate determination, and neural progenitor differentiation.

Dysregulation of GPSM1 has been implicated in a range of pathological conditions, making it an attractive target for basic research in oncology, neuroscience, and developmental biology. The availability of a recombinant form of this protein enables controlled biochemical and cell-based assays that would be difficult to perform using endogenous protein preparations.

Biochemical Properties of Recombinant Human GPSM1 Protein

Recombinant Human GPSM1 Protein (SKU: rp375069) is produced using recombinant expression systems to yield a protein that recapitulates the functional properties of the native human GPSM1 protein. Recombinant production enables consistent lot-to-lot reproducibility, defined purity levels, and the absence of contaminating human-derived pathogens — all critical considerations for reliable experimental outcomes.

Key biochemical characteristics of recombinant GPSM1 include its ability to bind GDP-Gαi subunits through its GoLoco motifs with high affinity, inhibit GTP loading onto Gαi, and interact with cytoskeletal-associated proteins via its TPR domain. These activities can be assessed using standard biochemical assays including co-immunoprecipitation, pull-down assays with recombinant Gα subunits, and fluorescence-based GTPase activity assays.

Users should consult the product datasheet (absea#PP-8802) for lot-specific information including molecular weight, purity by SDS-PAGE, endotoxin levels, recommended storage conditions, and reconstitution protocols. Proper handling and storage are essential to maintain protein activity over time.

Research Applications

Recombinant Human GPSM1 Protein is suitable for a broad range of research applications across multiple disciplines:

• G-protein Signaling Studies: Investigate the GDI activity of GPSM1 GoLoco motifs toward Gαi/o subunits, study competitive interactions between GPSM1 and Gβγ for Gα binding, and dissect the dynamics of G-protein activation cycles.
• Cell Polarity and Asymmetric Cell Division: Use recombinant GPSM1 as a tool to study the assembly of the cortical NuMA–LGN–Gαi ternary complex that governs mitotic spindle positioning and cortical force generation.
• Protein–Protein Interaction Assays: Employ recombinant GPSM1 in pull-down, SPR (surface plasmon resonance), or ITC (isothermal titration calorimetry) assays to map binding interfaces with Gα subunits, NuMA, or mInsc.
• Drug Discovery and Screening: Use as a biochemical tool to screen for small molecules or peptides that disrupt GPSM1–Gαi or GPSM1–NuMA interactions, with potential therapeutic relevance in oncology.
• Structural Biology: Serve as an antigen for antibody generation, or as a component in structural studies (e.g., cryo-EM, X-ray crystallography) of multi-protein complexes.
• Western Blot and ELISA Standards: Serve as a positive control or standard for immunodetection assays targeting GPSM1.

Handling, Storage, and Quality Considerations

To maximize the performance and shelf life of Recombinant Human GPSM1 Protein, researchers should adhere to the following general best practices, confirmed by the product-specific datasheet:

• Storage: Recombinant proteins are typically stored at –20°C or –80°C in a suitable buffer containing a carrier protein (e.g., BSA) and a cryoprotectant (e.g., glycerol) to prevent freeze-thaw denaturation. Always refer to the product datasheet for lot-specific storage instructions.
• Reconstitution: If supplied lyophilized, reconstitute with the recommended volume of sterile, ultrapure water or the specified buffer. Allow the vial to equilibrate to room temperature before opening, and mix gently by pipetting rather than vortexing.
• Aliquoting: To avoid repeated freeze-thaw cycles that can compromise protein integrity and activity, prepare single-use aliquots upon first use.
• Quality Control: Each lot of recombinant protein should be evaluated for purity (SDS-PAGE), identity (Western blot or mass spectrometry), and biological activity using a validated functional assay. Endotoxin levels should be assessed if the protein will be used in cell-based assays.
• Working Concentrations: Optimize the concentration of GPSM1 empirically for each specific assay format. Pilot experiments at multiple concentrations are recommended before committing to large-scale studies.

For specific lot data including purity percentage, activity units, endotoxin specification, and formulation details, users must consult the Certificate of Analysis (CoA) supplied with the product or available upon request from Aladdin Scientific.