Recombinant Dog Protein transport protein Sec61 subunit gamma (SEC61G)
Description
Fundamental Characteristics of SEC61G
The Sec61 complex serves as the central component of the protein translocation apparatus within the endoplasmic reticulum membrane. This complex consists of three membrane proteins: alpha (SEC61A), beta (SEC61B), and gamma (SEC61G) subunits . Together, these subunits form a transmembrane channel that facilitates the translocation of newly synthesized proteins across the ER membrane and their integration into the lipid bilayer.
SEC61G represents the gamma subunit of this complex and plays a crucial role in maintaining the structural integrity and functional capability of the protein translocon. While smaller than the alpha subunit, the gamma subunit is essential for proper channel formation and protein translocation activity . The Sec61 complex oligomerizes to form the transmembrane channel where proteins are translocated across and integrated into the ER membrane, with multiple SEC61G subunits contributing to this higher-order structure.
Molecular Structure and Conservation
The SEC61G protein in dogs exhibits high conservation with its counterparts in other mammalian species, reflecting its fundamental importance in cellular protein transport mechanisms. This conservation extends to the protein's structure, which features transmembrane domains that anchor it within the ER membrane. Though specific crystallographic data for dog SEC61G is limited, structural analyses of the Sec61 complex from other mammals provide valuable insights into its likely configuration and arrangement within the membrane environment.
Genetic Basis
Dog SEC61G is encoded by the SEC61G gene, which produces the gamma subunit protein through standard transcription and translation mechanisms. The gene contains coding sequences that determine the primary structure of the protein, including its transmembrane domains and interaction surfaces with other components of the translocation machinery . Alternative splicing variants encoding the same protein have been identified in mammalian systems, suggesting potential regulatory complexity in SEC61G expression.
Production of Recombinant Dog SEC61G
Recombinant dog SEC61G protein is typically produced using mammalian expression systems to ensure proper folding and post-translational modifications. While specific production parameters may vary between manufacturers, the general methodology involves cloning the dog SEC61G coding sequence into an appropriate expression vector, followed by transfection into mammalian host cells.
Expression Systems
Production of recombinant dog SEC61G typically utilizes mammalian cell lines such as HEK293 or Chinese Hamster Ovary (CHO) cells, which provide the appropriate cellular machinery for proper protein folding and processing. These expression systems are preferred over bacterial systems for membrane proteins like SEC61G to ensure native-like folding and insertion into membranes.
Purification Methods
Recombinant dog SEC61G is commonly produced with affinity tags, such as histidine (His) tags, to facilitate purification through affinity chromatography . The purification process typically involves:
-
Cell lysis under conditions that preserve protein structure
-
Membrane solubilization using appropriate detergents
-
Affinity chromatography using the incorporated tag
-
Size exclusion chromatography to separate aggregates and impurities
-
Quality control testing for purity and activity
Functional Role in Protein Transport Mechanisms
The SEC61G subunit plays a critical role in the function of the Sec61 complex, which serves as the central component of protein translocation machinery in the ER membrane.
Core Translocation Functions
The Sec61 complex facilitates several essential functions in protein transport:
-
Formation of the protein-conducting channel across the ER membrane
-
Recognition and binding of signal peptides on nascent proteins
-
Lateral gating to allow membrane protein integration into the lipid bilayer
-
Regulation of calcium efflux from the ER lumen
SEC61G contributes to these functions through its interactions with the other subunits of the complex and through contacts with the translocating polypeptide chain .
Stoichiometry in Functional Translocons
Electron microscopic analysis and biochemical studies suggest that between three and four heterotrimeric Sec61 complexes form the central unit of the protein translocase in the ER membrane . This oligomeric arrangement creates a central aqueous pore through which polypeptides can travel, while also providing a lateral opening for membrane protein integration.
In canine pancreatic microsomes, the stoichiometry of the Sec61 components has been quantitatively analyzed, revealing defined ratios that are essential for optimal translocation activity . These studies provide insight into how multiple SEC61G subunits contribute to the higher-order structure of active translocons.
Association with Other Translocon Components
The Sec61 complex does not function in isolation but associates with numerous additional proteins that enhance and regulate its activity. In native ER membranes, ribosome-associated Sec61 complexes are frequently found in complex with other components including:
-
Translocon-associated protein (TRAP) complex
-
Oligosaccharyltransferase (OST) complex
-
Translocating chain-associated membrane (TRAM) protein
-
Signal recognition particle receptor (SR)
-
Sec62 and Sec63 proteins
Recent cryoelectron tomography (CET) of native translocons has confirmed the permanent association of ribosome-associated Sec61 complexes with TRAP, with approximately 70% of translocon complexes in secretory cells also containing OST .
Applications in Research and Biotechnology
Recombinant dog SEC61G has numerous applications in scientific research and biotechnological developments.
Protein Transport Assays
Recombinant SEC61G can be incorporated into protein translocation assays to study the dynamics and kinetics of protein transport across membranes. These assays provide insights into how different signal sequences and polypeptide domains interact with the translocation machinery.
Drug Discovery and Development
The Sec61 complex has emerged as a potential target for therapeutic interventions in various diseases. For example, compounds like cotransin have been identified as substrate-selective Sec61 inhibitors that trap nascent transmembrane domains in the cytosolic vestibule of the channel . Recombinant dog SEC61G can be used in screening assays to identify and characterize new inhibitors with potential therapeutic applications.
Comparative Analysis with SEC61G from Other Species
The Sec61 complex is highly conserved across eukaryotic species, reflecting its fundamental importance in cellular protein transport. Comparative analysis of dog SEC61G with its counterparts from other species provides insights into evolutionary conservation and species-specific adaptations.
Sequence Homology
Dog SEC61G shares significant sequence homology with SEC61G proteins from other mammals, particularly with other canine species and closely related carnivores. This high degree of conservation reflects the crucial role of SEC61G in protein translocation, a process fundamental to cellular function.
Functional Conservation
Despite some sequence variations, the functional properties of SEC61G appear to be highly conserved across species. Studies comparing protein translocation in canine pancreatic microsomes with those from other species have shown remarkable similarities in the basic mechanisms of protein transport . This functional conservation underscores the evolutionary importance of maintaining proper protein translocation machinery.
Biochemical and Biophysical Properties
The biochemical and biophysical properties of recombinant dog SEC61G are critical for its function within the membrane environment.
Membrane Topology
As a component of the Sec61 complex, SEC61G is an integral membrane protein with defined transmembrane segments that anchor it within the ER membrane. The protein adopts a specific orientation relative to the membrane, with defined cytosolic and lumenal domains that facilitate interactions with other translocon components and translocating polypeptides.
Protein-Protein Interactions
SEC61G engages in multiple protein-protein interactions that are essential for translocon function. These include:
-
Interactions with SEC61A and SEC61B to form the heterotrimeric Sec61 complex
-
Contacts with other Sec61 complexes in the oligomeric translocon
-
Interactions with accessory factors that regulate translocation activity
-
Dynamic associations with nascent polypeptide chains during translocation
These interactions collectively determine the functional capacity of SEC61G within the translocation machinery.
Stability and Dynamics
The stability of recombinant dog SEC61G is influenced by its membrane environment and association with other translocon components. When purified and removed from its native membrane context, the protein typically requires stabilization through detergents or lipid nanodiscs to maintain its native conformation and activity.
Pathways and Functional Networks
SEC61G participates in several critical cellular pathways related to protein transport and processing.
Involved Biological Pathways
Based on studies of SEC61G in various mammalian systems, the protein is known to participate in several key pathways:
| Pathway Name | Role of SEC61G |
|---|---|
| Protein export | Core component of the translocation channel |
| Protein processing in endoplasmic reticulum | Facilitates entry of newly synthesized proteins into the ER lumen |
| Phagosome formation | Contributes to membrane remodeling during phagosome formation |
| Secretory protein synthesis | Essential for translocation of secretory proteins into the ER |
These pathways represent fundamental cellular processes required for normal physiology and homeostasis .
Associated Protein Networks
SEC61G functions within a complex network of proteins involved in protein synthesis, folding, and quality control. Key interacting partners include:
-
Signal recognition particle (SRP) and SRP receptor
-
Ribosomal proteins at the ER membrane
-
ER lumenal chaperones like BiP (immunoglobulin heavy chain binding protein)
-
Signal peptidase complex
-
Oligosaccharyltransferase complex
These interactions coordinate the sequential steps of protein synthesis, translocation, and processing in the ER .
Future Research Directions
Research on recombinant dog SEC61G continues to evolve, with several promising directions for future investigation.
Species-Specific Functions
Comparative studies between dog SEC61G and its counterparts from other species could reveal species-specific adaptations in protein translocation mechanisms. Such studies may have implications for understanding differences in drug responses and disease susceptibilities between species.
Therapeutic Applications
The Sec61 complex represents a potential target for therapeutic interventions in various diseases. Further research on dog SEC61G could contribute to the development of novel drugs targeting protein translocation for veterinary applications or as models for human therapeutics.
Product Specs
Note: While we prioritize shipping the format currently in stock, please specify your format preference in order notes for customized fulfillment.
Note: All proteins are shipped with standard blue ice packs unless dry ice shipping is requested in advance. Additional fees apply for dry ice shipping.
The tag type is determined during production. If you require a specific tag, please inform us, and we will prioritize its development.
Target Background
Q&A
What is the structural composition of canine SEC61G and how does it compare to human SEC61G?
Canine SEC61G is a small (~7.7 kDa) single-pass membrane protein that forms part of the heterotrimeric SEC61 complex alongside SEC61α and SEC61β subunits. The protein consists of 68 amino acids with a highly conserved sequence across mammalian species. Structural analysis reveals an α-helix-loop-α-helix secondary structure when associated with membrane environments . The amino acid sequence of canine SEC61G shows remarkable conservation with human SEC61G (P60059), particularly in functional domains. This high degree of sequence homology (predicted confidence score >80%) enables cross-species applications in many experimental systems .
What are the fundamental roles of SEC61G in cellular physiology?
SEC61G functions as an essential component of the SEC61 translocon complex that mediates transport of signal peptide-containing precursor polypeptides across the endoplasmic reticulum (ER) membrane . The gamma subunit specifically contributes to:
-
Structural stability of the SEC61 translocon complex
-
Facilitating the lateral gate opening for membrane protein insertion
-
Maintaining the seal that prevents unregulated ion leakage across the ER membrane
-
Supporting post-translational modifications of secretory and membrane proteins
Experimental evidence from recombinant systems demonstrates that while SEC61G is one of the smallest components of the translocon, it is essential for proper translocon assembly and function .
What expression systems are most effective for producing functional recombinant canine SEC61G?
Based on published methodologies, several expression systems have been successfully employed for recombinant canine SEC61G production:
| Expression System | Advantages | Limitations | Notable Applications |
|---|---|---|---|
| E. coli bacterial system | High yield, economical, simple setup | Lacks post-translational modifications, potential inclusion body formation | Structural studies, antibody production, protein-protein interaction studies |
| Baculovirus/Sf21 insect cells | Proper folding, higher stability, formation of functional complexes with SEC61α | More complex, higher cost, longer production time | Functional reconstitution, photo-affinity labeling, crosslinking studies |
| Mammalian cell expression | Native post-translational modifications, proper membrane insertion | Lowest yield, highest complexity | Advanced functional studies, trafficking analyses |
For functional studies requiring proper membrane integration, expression of SEC61G in complex with SEC61α in Sf21 insect cells has been demonstrated to yield stable complexes with approximately 1:1 stoichiometry that can bind cotransin analogs (CT7, CT8, CT9) similarly to native SEC61 complexes .
What purification strategies ensure optimal recovery of structurally intact recombinant canine SEC61G?
Effective purification of recombinant canine SEC61G requires specialized approaches due to its small size and hydrophobic nature. A recommended methodological workflow includes:
-
Expression tagging strategy: N-terminal FLAG-tag (3x-FLAG) fusion has been successfully employed for SEC61G purification without compromising function .
-
Membrane isolation: Following cell lysis (e.g., using microfluidizer at 15,000 psi), differential centrifugation isolates microsomal fractions (45,000 rpm in a type 70 Ti rotor for 1 hour at 4°C).
-
Nuclease treatment: Treatment with micrococcal nuclease (150 units/ml) at 25°C for 10 minutes removes endogenous RNA.
-
Detergent solubilization: Carefully selected detergents maintain the structural integrity of SEC61G, with dodecylphosphocholine showing particular efficacy for preserving the alpha-helical structure .
-
Affinity purification: Using anti-FLAG M2 affinity matrix followed by gentle elution conditions.
-
Quality assessment: Verification of proper folding through photo-affinity labeling with cotransin analogs and/or crosslinking assays with model substrates .
This purification approach has yielded recombinant SEC61α/γ complexes that behave functionally similar to native complexes in canine pancreatic microsomes.
How can researchers assess the functional integrity of recombinant canine SEC61G in experimental settings?
Multiple complementary approaches can verify the functional integrity of recombinant canine SEC61G:
-
Co-association assay: Stable association with SEC61α at ~1:1 stoichiometry indicates proper folding .
-
Photo-affinity labeling: Binding of cotransin probes (e.g., CT7) that can be competed by CT8 or CT9 verifies native-like conformation .
-
Crosslinking assays: BMH (bismaleimidohexane) crosslinking between cysteine residues in nascent chain models (e.g., TNFα 126-mers) and recombinant SEC61 complex demonstrates functional engagement .
-
Translocation assays: Using in vitro translation systems supplemented with recombinant SEC61-containing microsomes to assess translocation of model secretory proteins .
-
ER membrane permeability tests: Measuring ion or small molecule flux across membranes containing wild-type versus mutant SEC61 complexes can reveal functional defects in channel gating .
What methodological approaches are most effective for studying SEC61G-substrate interactions?
To investigate SEC61G interactions with translocation substrates, researchers should consider these advanced methodological approaches:
-
Site-specific photo-crosslinking: Incorporation of photo-activatable amino acids at defined positions within SEC61G or substrate proteins, followed by UV irradiation and mass spectrometry analysis.
-
Cryo-EM structural analysis: Recent advancements have allowed visualization of transmembrane domains passing through the SEC61 lateral gate during membrane insertion . This approach requires:
-
Preparation of stalled ribosome-nascent chain complexes
-
Reconstitution with purified SEC61 complexes
-
Single-particle cryo-EM data collection and processing
-
-
Mutational analysis: Systematic mutation of conserved residues in SEC61G followed by functional assays can map interaction surfaces. Cancer-associated mutations (e.g., R24I, K27E, I64T) provide naturally occurring variants for study .
-
FRET-based approaches: Fluorescently labeled SEC61G and substrate proteins can report on real-time interactions and conformational changes during translocation.
What is the relationship between SEC61G expression and glycolytic activity in cancer models, and how can this be experimentally verified?
Recent studies have established a significant positive correlation between SEC61G expression and glycolytic activity in multiple cancer types, including lung adenocarcinoma and breast cancer . To experimentally investigate this relationship:
-
Expression correlation analysis: Analyze correlation between SEC61G expression and glycolysis-related genes (ENO1, G6PD, LDHA, LDHB, PGK1, SLC2A1) in both public datasets and experimental models .
-
Metabolic flux measurement: After SEC61G knockdown or overexpression, measure:
-
FDG-PET imaging correlation: In clinical samples, correlate SEC61G expression with standardized uptake values (SUVs) from FDG-PET/CT scans, which reflect glucose metabolism in vivo .
-
Glycolytic enzyme activity assays: Directly measure the activities of key glycolytic enzymes after modulating SEC61G expression.
The experimental evidence indicates that SEC61G knockdown significantly reduces glycolytic activity in multiple cancer cell lines, suggesting a regulatory role in metabolic reprogramming that contributes to tumor progression .
What methodological approaches can effectively assess the impact of SEC61G on tumor immune microenvironment?
SEC61G has been implicated in regulating the tumor immune microenvironment and immune evasion . To investigate this function, researchers should employ these methodologies:
-
Immune cell infiltration analysis:
-
Immune checkpoint expression correlation:
-
Co-culture systems:
-
Tumor microenvironment scoring:
Research has demonstrated that SEC61G expression negatively correlates with infiltration of critical immune cell populations and is associated with immune checkpoint gene expression, suggesting its role in creating an immunosuppressive tumor microenvironment .
How does canine SEC61G function compare to human SEC61G in experimental models, and what are the implications for comparative oncology?
Comparative analysis of canine and human SEC61G reveals important insights for translational research:
-
Sequence and structural conservation: The high sequence homology between canine and human SEC61G (predicted confidence score >80%) suggests conserved functions across species.
-
Functional conservation: Both canine and human SEC61G play essential roles in:
-
Protein translocation across the ER membrane
-
Maintenance of ER membrane permeability barriers
-
Cancer-associated functions including glycolysis regulation and immune modulation
-
-
Disease relevance: SEC61G is implicated in similar cancer types in both species, making canine models valuable for studying human diseases.
The conservation of SEC61G structure and function between dogs and humans makes canine models potentially valuable for:
-
Testing SEC61G-targeted therapeutics before human clinical trials
-
Understanding fundamental mechanisms of SEC61G dysregulation in cancer
-
Developing diagnostic tools applicable across species
What technical considerations are essential when developing antibodies against canine SEC61G for research applications?
Development of effective antibodies against canine SEC61G requires attention to several technical considerations:
-
Epitope selection: The small size of SEC61G (68 amino acids) limits potential epitopes. Focus on:
-
Expression system for immunogen preparation:
-
Validation methodology matrix:
-
Western blot against recombinant protein and native tissue samples
-
Immunohistochemistry on fixed tissues with appropriate controls
-
Knockdown/knockout validation to confirm specificity
-
Cross-reactivity testing if relevant to experimental design
-
-
Application-specific optimization:
-
For western blot: Optimize sample preparation methods for membrane proteins
-
For IHC/IF: Determine optimal fixation and antigen retrieval methods
-
For IP: Test multiple lysis conditions to preserve protein-protein interactions
-
Available commercial antibodies, such as polyclonal rabbit anti-SEC61G antibodies, have been validated for multiple applications including western blot and IHC, with cross-reactivity to human, mouse, and rat proteins, and predicted reactivity to dog SEC61G .
What cryo-EM methodologies are most appropriate for studying the structural dynamics of canine SEC61G within the translocon complex?
Recent advances in cryo-EM have revolutionized our understanding of SEC61 complex dynamics. For optimal structural analysis of canine SEC61G:
-
Sample preparation considerations:
-
Data collection parameters:
-
Use energy filters to improve signal-to-noise ratio for membrane proteins
-
Employ strategies to address preferred orientation issues common with membrane protein complexes
-
Consider tilted data collection to improve angular distribution
-
-
Processing workflow:
-
Apply 3D classification to sort heterogeneous conformational states
-
Use focused refinement on the SEC61 complex to maximize local resolution
-
Consider time-resolved cryo-EM for capturing dynamic intermediate states
-
-
Validation approaches:
-
Perform crosslinking mass spectrometry to validate interfaces identified in cryo-EM maps
-
Use molecular dynamics simulations to analyze the stability of resolved conformations
-
Employ structure-based mutational analyses to confirm functional significance
-
Recent structural studies have revealed how transmembrane domains in a looped configuration pass through the SEC61 lateral gate during membrane insertion, providing templates for similar studies with canine SEC61G .
How can mutations identified in cancer-associated SEC61G variants be leveraged to understand channel gating mechanisms?
Cancer-associated mutations in SEC61G provide natural probes for understanding channel function and regulation:
-
Mutation mapping methodology:
-
Experimental characterization approaches:
-
Mechanistic investigation strategies:
-
Use site-specific crosslinking to determine if mutations alter interactions with other translocon components
-
Apply fluorescence-based assays to measure real-time changes in channel dynamics
-
Conduct cryo-EM analysis of wild-type versus mutant complexes to visualize structural changes
-
Research has demonstrated that cancer-associated mutations in SEC61G can alter the permeability of the translocon without compromising protein translocation function, suggesting these mutations specifically impact channel gating mechanisms that may contribute to malignancy .
