Recombinant Phaeosphaeria nodorum Golgi apparatus membrane protein TVP23 (TVP23)
Description
Overview of Phaeosphaeria nodorum
Phaeosphaeria nodorum (also known as Septoria nodorum) is a filamentous fungal pathogen that belongs to the Dothideomycete class, a major group of ascomycete fungi. The genome sequencing of P. nodorum strain SN15 was completed in 2007, marking it as the first fungal genome in the large Dothideomycete class to be fully sequenced . This organism has significant agricultural importance as the causative agent of glume blotch disease in wheat and other cereals, leading to substantial crop losses worldwide. The 37 Mb genome of P. nodorum encodes numerous secondary metabolite biosynthetic pathways, including 23 polyketide synthases, 14 nonribosomal peptide synthetases, and various other biosynthetic enzymes that contribute to its pathogenicity and ecological fitness . Understanding the cellular components and membrane proteins of this organism, including TVP23, provides valuable insights into its biology and potential interventions against its pathogenic effects.
The TVP23 Protein Family
The TVP23 protein from Phaeosphaeria nodorum belongs to the broader TVP23 protein family, which is evolutionarily conserved from yeast to humans . These proteins are characterized by their localization to the Golgi apparatus and their involvement in vesicular trafficking and membrane organization. In humans, the homologous protein TVP23B has been found to play critical roles in intestinal immunity and barrier function, with mutations in this gene conferring susceptibility to colitis . The conservation of this protein family across diverse organisms suggests fundamental roles in cellular homeostasis and membrane dynamics. TVP23 proteins typically contain multiple transmembrane domains that anchor them within the Golgi membrane, where they interact with other proteins to facilitate vesicle formation, trafficking, and fusion processes essential for proper cellular function.
Role of Golgi Apparatus Membrane Proteins
Golgi apparatus membrane proteins, including TVP23, serve as critical components in the secretory pathway of eukaryotic cells. These proteins facilitate the processing, sorting, and trafficking of cargo molecules through the highly organized cisternae of the Golgi complex. In the context of P. nodorum, Golgi membrane proteins likely contribute to the secretion of enzymes, effector proteins, and other virulence factors that enable the fungus to colonize host tissues and cause disease. TVP23 specifically functions in vesicular trafficking, potentially mediating the transport of proteins between different Golgi compartments or between the Golgi and other cellular destinations . This trafficking function is essential for maintaining cellular homeostasis, responding to environmental changes, and coordinating the complex processes of growth, development, and pathogenesis in fungal organisms. The study of these membrane proteins provides valuable insights into fundamental cellular processes and potential targets for intervention against fungal pathogens.
Protein Structure and Sequence
The Golgi apparatus membrane protein TVP23 from Phaeosphaeria nodorum is a full-length protein consisting of 194 amino acids . The complete amino acid sequence of this protein has been determined and is as follows: "METAQTAPAPGSLSWKLSSHPITLLTFLFFRISSLLVYLLGMRLLSSNFVLIFIVTILLLAMDFYYLKNIAGRRLVGLRWWNEVDGATGDGRWVFESADPESREQNATDKRFFWMALYVQPVLWVVMAVVALFGFNFIWLTLVAIALVLTITNTLAFSRCDKFSQASGFASNAMYGSGLARNLAGGLVSNWFRR" . This sequence reveals multiple hydrophobic regions consistent with its function as a transmembrane protein embedded within the Golgi membrane. Structural analysis suggests that TVP23 contains several transmembrane domains that traverse the lipid bilayer of the Golgi apparatus, with intervening loops that may participate in protein-protein interactions or other functional activities. The protein's structural features are highly adapted to its role in vesicular trafficking, allowing it to properly orient within the membrane and interact with other components of the trafficking machinery.
Molecular Weight and Physical Properties
The TVP23 protein from P. nodorum has a calculated molecular mass of approximately 21.8 kDa based on its amino acid composition . This relatively small size is typical of many membrane trafficking proteins, which often function as components of larger protein complexes rather than as individual enzymes. When expressed as a recombinant protein with an N-terminal histidine tag, the molecular weight may increase slightly due to the addition of the tag sequence. The physical properties of TVP23 are largely determined by its amino acid composition, which includes numerous hydrophobic residues that facilitate its integration into the Golgi membrane. The protein exists in a folded conformation that positions its hydrophobic segments within the lipid bilayer while allowing hydrophilic portions to interact with the aqueous environment on either side of the membrane. These structural arrangements are critical for the protein's stability and functional activity within the cellular context.
Protein Family Classification
TVP23 belongs to the TVP23 protein family, a group of evolutionarily conserved membrane proteins found across various eukaryotic organisms from fungi to humans . This family is characterized by their localization to the Golgi apparatus and their involvement in vesicular trafficking pathways. Members of this family share significant sequence homology and similar domain architectures, suggesting common functional mechanisms despite variations in specific cellular contexts. In humans, the related protein TVP23B has been shown to interact with another Golgi protein called YIPF6, forming complexes that regulate glycosylation enzyme distribution and intestinal barrier function . The conservation of these interactions across different species suggests that P. nodorum TVP23 may participate in similar protein-protein interactions within the fungal Golgi apparatus. The classification of TVP23 within this protein family provides a framework for understanding its likely functional roles and molecular mechanisms based on knowledge gained from better-characterized family members in model organisms.
Expression Systems and Vectors
The recombinant production of P. nodorum TVP23 has been primarily achieved using Escherichia coli expression systems, which provide an efficient platform for generating substantial quantities of the protein for research purposes . These expression systems typically employ specialized vectors that incorporate regulatory elements for controlling protein expression, affinity tags for purification, and sequences that optimize codon usage for the host organism. For TVP23 specifically, the full-length protein (amino acids 1-194) has been successfully expressed with an N-terminal histidine tag, facilitating downstream purification processes . The expression constructs used for TVP23 production are designed to maximize protein yield while maintaining proper folding and stability of this membrane protein in the bacterial environment. Although E. coli lacks the sophisticated membrane systems found in eukaryotic cells, it can still effectively produce many membrane proteins in forms suitable for biochemical and structural studies with appropriate optimization of expression conditions.
Purification Methods
The purification of recombinant P. nodorum TVP23 protein typically leverages the incorporated histidine tag, which enables efficient isolation through immobilized metal affinity chromatography (IMAC) . This method exploits the high affinity of histidine residues for divalent metal ions such as nickel or cobalt, allowing selective binding of the tagged protein to a metal-charged resin while contaminants are washed away. Following IMAC purification, additional chromatographic steps may be employed to achieve higher purity levels, often resulting in preparations with greater than 90% purity as determined by SDS-PAGE analysis . The purified protein is commonly provided in a lyophilized powder form, which enhances stability during storage and shipping . The development of effective purification protocols for TVP23 has been crucial for enabling biochemical characterization and functional studies of this membrane protein, providing researchers with high-quality material for diverse experimental applications.
Role in Vesicular Trafficking
The primary function of TVP23 in Phaeosphaeria nodorum appears to be its involvement in vesicular trafficking within the Golgi apparatus . As a membrane protein embedded in the Golgi complex, TVP23 likely participates in the formation, movement, or fusion of vesicles that transport cargo molecules between different cellular compartments. This trafficking function is essential for numerous cellular processes, including protein secretion, membrane recycling, and organelle maintenance. The specific mechanisms through which TVP23 contributes to vesicular trafficking may involve interactions with other trafficking proteins, lipid components of the Golgi membrane, or cytoskeletal elements that facilitate vesicle movement. Understanding these molecular interactions is crucial for elucidating the precise role of TVP23 in fungal cell biology and potentially identifying novel targets for antifungal interventions. The conservation of vesicular trafficking machinery across eukaryotes suggests that insights gained from studying P. nodorum TVP23 may have broader implications for understanding similar processes in other organisms.
Comparison with Homologs in Other Species
Research on TVP23 homologs in other species provides valuable context for understanding the potential functions of P. nodorum TVP23. In humans, the homologous protein TVP23B has been shown to play critical roles in intestinal immunity and barrier function . Specifically, TVP23B controls the homeostasis of Paneth cells and the function of goblet cells, leading to the production of antimicrobial peptides and the formation of a protective mucus layer that separates host tissues from the intestinal microbiota . Mutations in the TVP23B gene confer susceptibility to chemically induced and infectious colitis, highlighting its importance in maintaining intestinal health . Additionally, human TVP23B interacts with another Golgi protein called YIPF6, which is similarly crucial for intestinal homeostasis . This interaction appears to be functionally significant, as both proteins influence the distribution of glycosylation enzymes within the Golgi proteome . The conservation of these interactions and functions across diverse organisms suggests that P. nodorum TVP23 likely participates in analogous processes within the fungal cell, potentially contributing to membrane organization, protein trafficking, and cellular homeostasis in ways that are critical for fungal growth and pathogenicity.
Potential Biological Significance
The biological significance of TVP23 in Phaeosphaeria nodorum likely extends beyond its basic role in vesicular trafficking to influence broader aspects of fungal physiology and pathogenicity. As a component of the secretory pathway, TVP23 may indirectly affect the production and delivery of virulence factors that enable P. nodorum to infect host plants and cause disease. The proper functioning of the Golgi apparatus is essential for the glycosylation and processing of secreted proteins, many of which contribute to fungal cell wall integrity, nutrient acquisition, and host interaction. Disruptions in TVP23 function could potentially alter these processes, affecting the fungus's ability to survive in different environments or cause disease. Additionally, the involvement of TVP23 homologs in maintaining cellular homeostasis in other organisms suggests that this protein may play similar roles in P. nodorum, contributing to the fungus's ability to respond to environmental stresses and maintain internal balance. Understanding these broader biological implications of TVP23 function provides valuable context for interpreting experimental findings and identifying potential applications for this knowledge in agricultural or medical settings.
Potential Applications
The study of P. nodorum TVP23 holds potential for various applications, particularly in agricultural and biotechnological contexts. As a component of a significant plant pathogen, understanding TVP23 function could contribute to the development of novel strategies for controlling wheat glume blotch disease, potentially through the design of specific inhibitors that disrupt TVP23-dependent processes. In biotechnology, insights into the vesicular trafficking mechanisms mediated by TVP23 could inform the engineering of fungal strains with enhanced secretion capabilities for industrial enzyme production. Additionally, the structural and functional characterization of TVP23 contributes to the broader knowledge base of membrane protein biology, which has implications for understanding similar proteins in human health and disease. The recombinant TVP23 protein itself serves as a valuable research tool for antibody production, protein-protein interaction studies, and structural analyses that may reveal new aspects of Golgi apparatus function across different organisms. These diverse applications underscore the importance of basic research on fungal membrane proteins like TVP23 for addressing practical challenges in agriculture, medicine, and industrial biotechnology.
Areas for Future Investigation
Numerous avenues remain for future investigation of P. nodorum TVP23, including more detailed structural analyses using techniques such as X-ray crystallography or cryo-electron microscopy to elucidate its three-dimensional configuration within the membrane. Functional studies using gene knockout or knockdown approaches would help clarify the specific roles of TVP23 in fungal growth, development, and pathogenicity. Protein-protein interaction studies, perhaps using techniques like co-immunoprecipitation or yeast two-hybrid screening, could identify binding partners of TVP23 and provide insights into its position within larger protein networks that regulate vesicular trafficking. Comparative analyses with TVP23 homologs from other fungal species could reveal evolutionary adaptations related to different ecological niches or pathogenic lifestyles. Additionally, investigating the potential role of TVP23 in fungal responses to environmental stresses or antifungal agents might uncover new aspects of its biological significance and relevance to disease control strategies. These future research directions would collectively contribute to a more comprehensive understanding of TVP23 and its importance in fungal biology, potentially leading to practical applications in agriculture, medicine, or biotechnology.
Product Specs
Please note: We prioritize shipping the format currently in stock. However, if you have specific format requirements, please indicate them during order placement, and we will accommodate your request.
Please note: All proteins are shipped with standard blue ice packs by default. If you require dry ice shipping, please inform us in advance as additional fees will apply.
Generally, the shelf life of liquid form is 6 months at -20°C/-80°C. Lyophilized form has a shelf life of 12 months at -20°C/-80°C.
Target Background
KEGG: pno:SNOG_04371
Q&A
How is TVP23 protein conserved across species?
TVP23 belongs to a family of proteins that shows remarkable evolutionary conservation from yeast to mammals. The Tvp23 protein was initially identified in yeast Saccharomyces cerevisiae through proteomic analysis of Golgi subcompartments. Conserved sequences of TVP23 have been found across multiple species including plants (Arabidopsis homolog called Echidna) and mammals (TVP23B) . Despite this conservation, many of these homologs remained uncharacterized until recently. In yeast, TVP23 functions in retrograde transport between early endosomes and the late Golgi, while in mammals, TVP23B plays critical roles in intestinal homeostasis by controlling Paneth cells and goblet cell function . This functional conservation suggests TVP23 serves fundamental cellular roles that have been maintained throughout evolution.
What are the recommended storage and handling conditions for recombinant TVP23 protein?
For optimal stability and activity of recombinant TVP23 protein, researchers should follow these methodological guidelines:
| Parameter | Recommendation |
|---|---|
| Storage Temperature | -20°C/-80°C upon receipt |
| Aliquoting | Necessary for multiple use to prevent degradation |
| Reconstitution Buffer | Deionized sterile water |
| Recommended Concentration | 0.1-1.0 mg/mL |
| Glycerol Addition | 5-50% (final concentration) for long-term storage |
| Default Glycerol Concentration | 50% |
| Storage Buffer | Tris/PBS-based buffer with 6% Trehalose, pH 8.0 |
| Freeze-Thaw Cycles | Avoid repeated cycles; working aliquots can be stored at 4°C for up to one week |
Before opening the vial, it should be briefly centrifuged to bring contents to the bottom. Repeated freezing and thawing is not recommended as it may lead to protein denaturation and loss of activity .
What experimental approaches can be used to study TVP23 function in vesicular trafficking?
To investigate TVP23's role in vesicular trafficking, researchers can employ several complementary experimental approaches:
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Genetic Interaction Studies: Creating double mutants combining tvp23 deletion with mutations in SNARE proteins (such as vti1-2) can reveal functional relationships. For example, deletion of TVP23 was shown to aggravate the growth defect in vti1-2 cells, suggesting a cooperative function in retrograde transport .
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Fluorescence Microscopy with Tagged Proteins: Using GFP-tagged cargo proteins like GFP-Snc1p to track retrograde transport from early endosomes to the late Golgi. In vti1-2 cells, GFP-Snc1p accumulated within the cell, indicating defective retrograde transport, and this phenotype was exacerbated when TVP23 was also deleted .
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Immunoprecipitation and Interaction Networks: Immunoprecipitation studies have revealed that Tvp23, along with Tvp18 and Tvp15, exists in an interactive network with Yip1-family proteins (Yip4 and Yip5), suggesting they collectively maintain late Golgi/endosomal compartment function .
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Subcellular Fractionation and Localization: Immunofluorescence double staining of HA-tagged Tvp proteins and myc-tagged tSNAREs confirms the localization of these proteins in Tlg2-containing compartments .
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Synthetic Genetic Arrays: Disruptions of tvp15 and tvp23 showed synthetic aggravation with ypt6 or ric1 null mutations, further supporting their role in Golgi-related functions .
How does TVP23 interact with SNARE proteins in retrograde transport?
TVP23 demonstrates significant genetic interactions with the SNARE protein Vti1p, particularly with the vti1-2 allele, in the yeast Saccharomyces cerevisiae. These interactions are allele-specific, as TVP23 overexpression suppresses the growth defect in vti1-2 cells but not in vti1-11 cells .
The interaction between TVP23 and Vti1p specifically affects retrograde transport from the early endosome to the late Golgi, rather than forward transport. This was evidenced by the following experimental observations:
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When examining GFP-Snc1p (a marker for retrograde transport), vti1-2 cells showed intracellular accumulation, indicating defective recycling from early endosomes to the late Golgi.
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Deletion of TVP23 in vti1-2 cells (creating a double mutant) resulted in a synthetic defect in GFP-Snc1p recycling, whereas tvp23Δ cells alone showed only a slight defect.
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The vti1-11 cells, which did not respond to TVP23 overexpression, had normal retrograde transport, explaining the allele-specific nature of the genetic interaction .
These findings suggest that TVP23 performs a partially redundant function with Vti1p in retrograde transport, providing a "backup" mechanism when Vti1p function is compromised in specific ways. The molecular basis of this interaction likely involves TVP23's role in vesicle formation or targeting at the early endosome, complementing SNARE-mediated fusion at the late Golgi.
What are the differences in function between fungal TVP23 and mammalian TVP23B?
While both fungal TVP23 and mammalian TVP23B are conserved Golgi membrane proteins, their characterized functions reveal both similarities and distinct tissue-specific roles:
| Parameter | Fungal TVP23 | Mammalian TVP23B |
|---|---|---|
| Cellular Localization | Late Golgi/Tlg2-containing compartments | Trans-Golgi network |
| Primary Function | Retrograde transport from early endosome to late Golgi | Intestinal epithelial homeostasis |
| Interacting Partners | SNARE protein Vti1p, Yip4, Yip5 | YIPF6 (Golgi protein) |
| Phenotype of Deficiency | Mild growth defects, synthetic with SNARE mutations | Susceptibility to colitis, disrupted intestinal barrier |
| Molecular Mechanism | Assists in vesicular trafficking | Controls Paneth cell homeostasis and goblet cell function |
| Impact on Secretion | Minimal effect on vacuolar enzyme processing | Decrease in antimicrobial peptides, altered mucus layer |
| Essentiality | Nonessential for growth under laboratory conditions | Critical for intestinal epithelial function |
In mammals, TVP23B has evolved specialized functions related to the intestinal epithelium. TVP23B-deficient mice show hypersensitivity to DSS-induced colitis, with greater weight loss, increased disease activity, diarrhea, rectal bleeding, and colonic shortening . At the molecular level, TVP23B binds with another Golgi protein, YIPF6, and affects the Golgi proteome, particularly glycosylation enzymes critical for intestinal homeostasis .
What methodological approaches can be used to generate TVP23 mutants for functional studies?
Researchers have successfully employed several approaches to generate TVP23 mutations for functional studies:
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CRISPR/Cas9 Gene Editing: This technique was used to generate a 1 bp frameshift allele of the Tvp23b gene in mice. The resulting Tvp23b−/− mice exhibited increased susceptibility to DSS challenge, confirming TVP23B's role in intestinal homeostasis .
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Conditional Alleles: For tissue-specific studies, researchers generated a conditional allele targeting exon 2 of TVP23B, which creates a frameshift mutation when deleted. By crossing these mice with Villin-Cre mice, they created intestinal epithelium-specific deletions (Tvp23bFL/FL; Villin-CRE), demonstrating TVP23B's requirement in the intestinal epithelium .
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Yeast Genetics: In yeast, researchers have used standard deletion approaches to create tvp23Δ strains, which were then combined with temperature-sensitive alleles of interacting partners (like vti1-2) to study genetic interactions .
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Multicopy Suppression Analysis: Overexpression of TVP23 was used to identify genetic interactions, such as the suppression of growth defects in vti1-2 cells but not vti1-11 cells, revealing allele-specific interactions .
These methodological approaches demonstrate the versatility of genetic tools available for studying TVP23 function across different model systems, from yeast to mammals, allowing researchers to dissect its role in different cellular contexts.
How can researchers investigate TVP23's role in protein glycosylation and trafficking?
TVP23 and its mammalian homolog TVP23B have been implicated in glycosylation processes through their association with Golgi function. To investigate this role, researchers can employ the following methodological approaches:
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Golgi Proteome Analysis: Mass spectrometry-based comparison of Golgi proteomes from wild-type versus TVP23-deficient cells can reveal changes in glycosylation enzymes. Studies of TVP23B and YIPF6-deficient colonocytes showed common deficiencies in several critical glycosylation enzymes .
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Glycoprotein Processing Assays: Monitoring the processing of model glycoproteins such as carboxypeptidase Y and alkaline phosphatase. Although tvp disruptants in yeast showed normal processing of these enzymes , more sensitive assays might reveal subtle defects in glycosylation patterns.
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Mucin Layer Analysis: In intestinal epithelial cells, assessing the formation and penetrability of the mucus layer, which depends on proper glycosylation. TVP23B-deficient mice showed a more penetrable mucus layer with decreased antimicrobial peptides .
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Immunofluorescence Co-localization: Using antibodies against glycosylation enzymes and TVP23 to determine their co-localization within Golgi subcompartments.
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Trafficking of Glycosylation Enzymes: Using fluorescently tagged glycosylation enzymes to track their movement and retention in the Golgi in the presence or absence of TVP23.
These approaches can help elucidate TVP23's role in maintaining the proper localization and function of glycosylation machinery, which is critical for many cellular processes including secretion, membrane integrity, and cell-cell communication.
