Recombinant Pongo abelii FERM domain-containing protein 3 (FRMD3)

What is FRMD3 and what is its structural characterization?

FRMD3 (FERM domain-containing protein 3) is a protein that belongs to the FERM domain-containing family. In Pongo abelii (Sumatran orangutan), FRMD3 is composed of 597 amino acids with a molecular structure that includes a characteristic FERM domain. The protein contains several functional regions, including an N-terminal ubiquitin-like domain that is crucial for protein-protein interactions. The full amino acid sequence of Pongo abelii FRMD3 begins with MFASCHCVPRGRRTMKMIHFRSSSIKSLSQEMRCTIRLLDDSEISCHIQRETKGQFLIDH and continues through its 597-amino acid length . The FERM domain is a conserved structural motif found in many proteins involved in cytoskeletal organization and cellular signaling, making FRMD3 potentially important in cellular structural integrity and signaling pathways.

What are the optimal storage and handling conditions for Recombinant Pongo abelii FRMD3?

For optimal stability and activity maintenance of Recombinant Pongo abelii FRMD3, the protein should be stored at -20°C for routine use, or at -80°C for extended storage periods. The recombinant protein is typically supplied in a Tris-based buffer containing 50% glycerol, specifically optimized for this protein . Researchers should note that repeated freezing and thawing cycles significantly compromise protein integrity and should be avoided. For short-term use (up to one week), working aliquots can be maintained at 4°C . When reconstituting lyophilized FRMD3, it is recommended to briefly centrifuge the vial prior to opening and then reconstitute in deionized sterile water to a concentration of 0.1-1.0 mg/mL, potentially with the addition of 5-50% glycerol as a cryoprotectant for long-term storage .

How does the amino acid sequence of Pongo abelii FRMD3 compare with human FRMD3?

Comparative analysis of Pongo abelii and human FRMD3 reveals high sequence homology, reflecting their evolutionary relationship. Both proteins contain 597 amino acids and share key structural components including the FERM domain. The human FRMD3 sequence (UniProt ID: A2A2Y4) differs from the Pongo abelii sequence (UniProt ID: Q5R803) at several positions, though the functional domains remain highly conserved .

A specific difference can be observed at position 4 of the amino acid sequence where Pongo abelii FRMD3 has an isoleucine (I) while human FRMD3 has a valine (V): "MFASCHCVPRGRRTMKMIHFRSSSIKSLSQE..." in Pongo abelii versus "MFASCHCVPRGRRTMKMIHFRSSSVKSLSQE..." in human . This high degree of conservation suggests that findings from studies using Pongo abelii FRMD3 may have translational relevance to human biology and disease.

What expression systems are recommended for producing functional Recombinant FRMD3?

For the production of functional Recombinant FRMD3, both prokaryotic and eukaryotic expression systems have been employed with varying advantages. E. coli-based expression systems have been successfully used for producing recombinant human FRMD3, resulting in sufficient protein yields for structural and functional studies . This bacterial system is particularly advantageous for obtaining high quantities of protein for initial characterization and antibody production. For Pongo abelii FRMD3, similar prokaryotic expression strategies can be applied, with optimization of codon usage to enhance expression levels.

For studies requiring post-translational modifications and proper protein folding, eukaryotic expression systems such as mammalian cell lines (HEK293, CHO) or insect cell lines may be preferable, though these are not explicitly mentioned in the search results. When designing expression constructs, researchers should carefully consider the addition of purification tags (such as His-tag or GST-tag) and their potential impact on protein function, especially when studying protein-protein interactions involving the N-terminal domain .

What analytical techniques are optimal for studying FRMD3-protein interactions?

For investigating FRMD3-protein interactions, several complementary techniques have proven effective. Co-immunoprecipitation (Co-IP) has been successfully employed to identify FRMD3's interaction with vimentin and ubiquitin protein ligase E3A (UBE3A) . When studying the interaction between FRMD3 and vimentin specifically, researchers have utilized domain mapping approaches to identify the N-terminal ubiquitin-like domain of FRMD3 as the critical region for binding to the head domain of vimentin .

Protein-protein interaction studies can be further validated using proximity ligation assays (PLA) or fluorescence resonance energy transfer (FRET) techniques to confirm direct interactions in cellular contexts. For in vitro verification of direct binding, surface plasmon resonance (SPR) or isothermal titration calorimetry (ITC) would provide quantitative binding kinetics data. When investigating the functional consequences of these interactions, such as the FRMD3-mediated degradation of vimentin, ubiquitination assays and proteasome inhibition experiments have proven informative .

What mechanisms underlie FRMD3's tumor suppressor function in cancer models?

FRMD3 exhibits potent tumor suppressor activity, particularly in breast cancer (BRCA) models, through several interconnected molecular mechanisms. Research has demonstrated that FRMD3 is significantly downregulated in breast cancer clinical tissue and cell lines, with this reduced expression strongly correlating with disease progression and shortened patient survival . The tumor-suppressive function of FRMD3 operates through its ability to inhibit cancer cell proliferation, migration, and invasion both in vitro and in vivo.

The primary mechanism involves FRMD3's interaction with vimentin and ubiquitin protein ligase E3A (UBE3A), which induces polyubiquitin-mediated proteasomal degradation of vimentin. This degradation subsequently leads to downregulation of focal adhesion complex proteins and inhibition of pro-cancerous signaling activation . These molecular changes result in cytoskeletal rearrangement and defects in cell morphology and focal adhesion, ultimately restricting cancer cell mobility and invasive capacity. The N-terminal ubiquitin-like domain of FRMD3 is particularly crucial for this function, as it binds directly to the head domain of vimentin; truncated FRMD3 lacking this domain shows almost complete loss of anti-cancer effects .

What experimental approaches are most effective for studying FRMD3 function in vivo?

For mechanistic studies, conditional knockout or knockin animal models targeting FRMD3 would provide valuable insights, though these are not explicitly described in the search results. When assessing FRMD3's impact on metastasis specifically, experimental designs should include both primary tumor growth measurements and quantification of distant metastatic burden. Tissue-specific expression analysis in normal versus diseased states can be achieved through immunohistochemistry (IHC) and in situ hybridization techniques, providing context for functional observations.

How can truncated or mutated versions of FRMD3 be used to study domain-specific functions?

Domain-specific functional analysis of FRMD3 can be effectively conducted using truncated or mutated protein variants. Studies have successfully employed this approach to identify the N-terminal ubiquitin-like domain as the critical region for FRMD3-vimentin interaction . When designing such experiments, researchers should create a systematic series of truncation mutants that selectively remove specific domains while maintaining the structural integrity of remaining regions.

Site-directed mutagenesis of key residues within identified functional domains can further refine understanding of specific amino acids critical for protein-protein interactions or enzymatic functions. For the ubiquitin-like domain specifically, mutation of conserved residues involved in typical ubiquitin-like protein interactions would help distinguish between structural and functional roles of this domain. Complementation assays, where truncated FRMD3 constructs are expressed in FRMD3-knockdown cells, can directly assess which domains are necessary and sufficient for specific cellular functions, such as suppression of migration or proliferation .

What evolutionary insights can be gained from studying Pongo abelii FRMD3 compared to other primates?

Comparative analysis of FRMD3 across primate species offers valuable evolutionary insights, particularly given the unique life history traits of orangutans. Pongo abelii (Sumatran orangutan) exhibits lower reproductive rates than other hominoids and slower growth rates than most primates except humans . These distinctive traits may be linked to evolutionary adaptations in various molecular pathways, potentially including those involving FRMD3.

How do metabolic adaptations in orangutans potentially impact FRMD3 function and expression?

Orangutans exhibit unique metabolic adaptations for low energy throughput, which may influence the function and expression of various proteins, including FRMD3. While direct evidence linking orangutan metabolic adaptations to FRMD3 expression is not presented in the search results, this represents an intriguing area for future research. Orangutans demonstrate lower daily energy expenditure than humans and other mammals, suggesting evolutionary decreases in energy throughput . This metabolic adaptation may be reflected in the regulation and activity of proteins involved in cellular energetics and growth control pathways.

Given FRMD3's role in regulating cell proliferation and cytoskeletal organization in humans , its function in orangutans may be adapted to their unique metabolic profile. Potential research questions could explore whether FRMD3 expression correlates with tissue-specific metabolic rates in orangutans, or if its interactions with cytoskeletal proteins like vimentin contribute to energy-conserving cellular adaptations. Comparative studies examining FRMD3 expression in tissues with different metabolic demands across primate species could provide insights into how this protein may have adapted to species-specific energy utilization strategies.