Recombinant Chicken Solute carrier family 25 member 36 (SLC25A36)

What is the basic structure and function of chicken SLC25A36? [BASIC]

Chicken Solute carrier family 25 member 36 (SLC25A36) is a mitochondrial carrier protein consisting of 313 amino acids. The full amino acid sequence is: MSQRDTLVHLFAGGCGGTVGAILTCPLEVVKTRLQSSSVTLYISEVHLNTVNGASVNRVTRVSPGPLHCLKMILQKEGPRSLFRGLGPNLVGVAPSRAIYFAAYSNCKEKLNNIFNPDSTQVHMISAGVAGFTAITMTNPIWLVKTRLQLDARNRGEKRMSAFECVRKVYRSDGIKGFYRGMSASYAGISETVIHFVIYESIKRKLLEHKTASAMDSEDESAKEASDFVGMMMAAATSKTCATSIAYPHEVVRTRLREEGTKYRSFFQTLSLLVREEGYGSLYRGLTTHLVRQIPNTAIMMSTYEVVVYLLDG .

Functionally, SLC25A36 serves as a transmembrane transporter located in the mitochondrial inner membrane . Its primary role involves the transport of pyrimidine nucleotides across the mitochondrial membrane, which is essential for mitochondrial DNA and RNA metabolism . Specifically, it transports cytosine and uracil (deoxy)nucleoside mono-, di-, and triphosphates via both uniport and antiport mechanisms .

How does chicken SLC25A36 compare to its human ortholog? [ADVANCED]

Chicken SLC25A36 shares significant structural and functional homology with its human ortholog. While the chicken version consists of 313 amino acids, both proteins belong to the SLC25 family of mitochondrial carriers . Functionally, both proteins are involved in pyrimidine nucleotide transport across the mitochondrial membrane.

The human SLC25A36 has been characterized as a mitochondrial transporter that primarily handles cytosine and uracil (deoxy)nucleoside mono-, di-, and triphosphates through both uniport and antiport mechanisms . This differs slightly from another human family member, SLC25A33, which transports uracil, thymine, and cytosine (deoxy)nucleoside di- and triphosphates exclusively via antiport .

This conservation of function across species highlights the evolutionary importance of these mitochondrial transporters for essential cellular processes, particularly those involving mitochondrial DNA and RNA synthesis and breakdown .

What expression systems are optimal for recombinant chicken SLC25A36 production? [BASIC]

Based on successful production strategies, E. coli has been demonstrated as an effective expression system for recombinant chicken SLC25A36. The commercial preparation available uses E. coli to express the full-length protein (amino acids 1-313) with an N-terminal His tag . This system provides several advantages for research purposes:

• High yield protein production

• Relatively simple culture conditions

• Compatibility with His-tag purification methods

• Established protocols for membrane protein expression

When expressing SLC25A36 in E. coli, researchers should optimize culture conditions including temperature, induction parameters, and media composition to enhance soluble protein yield. Since SLC25A36 is naturally a membrane protein, expression strategies that address potential toxicity and inclusion body formation are critical .

What are the optimal purification and reconstitution methods for functional studies of SLC25A36? [ADVANCED]

For functional characterization of SLC25A36, a multi-step purification and reconstitution approach is recommended:

• Initial purification: Affinity chromatography using the His-tag is the primary purification method, typically employing immobilized metal affinity chromatography (IMAC) .

• Buffer optimization: The purified protein should be maintained in a stabilizing buffer. For SLC25A36, a Tris/PBS-based buffer with 6% trehalose at pH 8.0 has been successfully used .

• Reconstitution in liposomes: For functional transport studies, the purified protein should be reconstituted into liposomes. This approach has been successfully used for characterizing the transport properties of human SLC25A33 and SLC25A36 .

• Storage considerations: After purification, the protein is typically stored as a lyophilized powder. Upon reconstitution, it should be stored at -20°C/-80°C with 5-50% glycerol to maintain stability. Aliquoting is recommended to avoid repeated freeze-thaw cycles .

The reconstitution in liposomes is particularly critical for transport assays, as it allows for the creation of a controlled environment to measure substrate transport across membranes, mimicking the mitochondrial inner membrane where SLC25A36 naturally functions .

What substrates does chicken SLC25A36 transport across mitochondrial membranes? [BASIC]

Based on characterization of the human ortholog, chicken SLC25A36 is expected to primarily transport pyrimidine nucleotides. Specifically, it likely transports:

• Cytosine nucleotides (mono-, di-, and triphosphates)

• Uracil nucleotides (mono-, di-, and triphosphates)

• Possibly thymine nucleotides, though with different efficiency

While the chicken-specific transport kinetics have not been directly reported in the search results, the human ortholog shows capability for transporting certain guanine nucleotides but not adenine (deoxy)nucleotides . This substrate specificity suggests a specialized role in pyrimidine nucleotide metabolism rather than general nucleotide transport.

What are the kinetic parameters and transport mechanisms of SLC25A36? [ADVANCED]

The transport mechanism of SLC25A36 involves both uniport (single substrate transport) and antiport (exchange of substrates) of pyrimidine nucleotides across the mitochondrial inner membrane . This contrasts with SLC25A33, which operates exclusively through antiport mechanisms.

Key kinetic characteristics of SLC25A36 transport include:

• Saturable transport: The carrier exhibits saturable kinetics, indicating a finite number of binding sites and a conventional Michaelis-Menten type transport mechanism .

• Inhibition profile: Transport is inhibited by mercurial compounds and other inhibitors of mitochondrial carriers, though with varying degrees of sensitivity .

• Substrate specificity: SLC25A36 shows preference for cytosine and uracil nucleotides in different phosphorylation states (mono-, di-, and triphosphates) with limited transport of guanine nucleotides and no significant transport of adenine nucleotides .

These transport properties enable SLC25A36 to facilitate the bidirectional movement of pyrimidine nucleotides between the cytosol and mitochondrial matrix, supporting mitochondrial genome replication and transcription processes .

What methods are used to verify mitochondrial localization of SLC25A36? [BASIC]

Several complementary techniques can be employed to verify the mitochondrial localization of SLC25A36:

• Subcellular fractionation: Isolation of mitochondria followed by Western blotting to detect SLC25A36 in the mitochondrial fraction.

• Immunofluorescence microscopy: Using antibodies against SLC25A36 and co-staining with mitochondrial markers (such as MitoTracker) to demonstrate co-localization.

• Expression of tagged proteins: Expressing SLC25A36 fused to fluorescent proteins (e.g., GFP) to visualize its cellular localization in live cells.

• Protease protection assays: To determine the membrane topology and confirm integration into the mitochondrial inner membrane.

• Functional complementation studies: As demonstrated with the human ortholog, expressing SLC25A36 in yeast cells lacking the endogenous mitochondrial pyrimidine nucleotide carrier (RIM2) and demonstrating functional rescue provides additional evidence for mitochondrial localization and function .

The search results specifically mention that both SLC25A33 and SLC25A36 "were found to be targeted to mitochondria," confirming their mitochondrial localization .

How can transport activity of SLC25A36 be measured in reconstituted systems? [ADVANCED]

Measuring the transport activity of SLC25A36 in reconstituted systems requires several specialized techniques:

• Liposome reconstitution: The purified SLC25A36 protein should be incorporated into liposomes composed of defined phospholipids to create proteoliposomes .

• Substrate loading: The proteoliposomes can be preloaded with specific substrates (e.g., various pyrimidine nucleotides) to establish a concentration gradient.

• Transport assays: Several approaches can be used:

  • Radiolabeled substrate uptake/efflux measurements

  • Fluorescent substrate analogs with spectroscopic detection

  • Indirect coupling assays that link transport to detectable reactions

• Inhibitor studies: Testing the effects of known mitochondrial carrier inhibitors (like mercurial compounds) on transport rates provides further characterization .

• Kinetic analysis: Determining transport rates at varying substrate concentrations to establish parameters such as Km, Vmax, and substrate specificity.

The methodology described in the literature for human SLC25A36 involved "direct assays in reconstituted liposomes" to demonstrate the transport of pyrimidine nucleotides . This approach provides the most direct evidence of transport function and specificity.

How conserved is SLC25A36 across different species? [BASIC]

SLC25A36 shows remarkable evolutionary conservation across various species, indicating its fundamental importance in cellular metabolism. Based on the search results, orthologs have been identified in multiple vertebrate and invertebrate species:

This conservation across diverse species spanning vertebrates and invertebrates suggests that SLC25A36 plays an essential evolutionary conserved role in cellular functions, particularly in mitochondrial nucleotide transport and metabolism .

What functional differences exist between SLC25A36 and its closest paralog SLC25A33? [ADVANCED]

Though both SLC25A36 and SLC25A33 are mitochondrial carriers that transport pyrimidine nucleotides, they exhibit several important functional differences:

• Transport mechanism:

  • SLC25A36 functions through both uniport and antiport mechanisms

  • SLC25A33 operates exclusively through antiport mechanisms

• Substrate specificity:

  • SLC25A36 transports cytosine and uracil (deoxy)nucleoside mono-, di-, and triphosphates

  • SLC25A33 transports uracil, thymine, and cytosine (deoxy)nucleoside di- and triphosphates, but not monophosphates

• Efficiency: The two carriers likely transport their substrates with different efficiencies, suggesting complementary rather than redundant roles .

These differences in transport mechanisms and substrate preferences indicate that SLC25A33 and SLC25A36 likely have distinct physiological roles in maintaining the mitochondrial nucleotide pool, potentially responding to different cellular conditions or metabolic states .

What is the role of SLC25A36 in mitochondrial DNA and RNA metabolism? [BASIC]

SLC25A36 plays a crucial role in mitochondrial nucleic acid metabolism by facilitating the transport of essential pyrimidine nucleotides across the mitochondrial inner membrane . This function is vital because:

• DNA replication support: Mitochondria contain their own genome (mtDNA) that requires nucleotides for replication. SLC25A36 helps supply necessary pyrimidine building blocks for this process.

• RNA synthesis: Mitochondrial gene expression involves transcription within the organelle, requiring a steady supply of nucleotides that SLC25A36 helps maintain.

• Nucleotide pool balance: By transporting pyrimidine nucleotides in both directions (through uniport and antiport mechanisms), SLC25A36 helps maintain an optimal balance of nucleotide concentrations between the cytosol and mitochondrial matrix .

• Metabolic coordination: The transport function connects cytosolic and matrix biochemical pathways, coordinating nuclear and mitochondrial genome maintenance and expression .

The search results specifically state that SLC25A33 and SLC25A36 are "essential for mitochondrial DNA and RNA metabolism" and their main physiological role is to "import/export pyrimidine nucleotides into and from mitochondria," highlighting their critical function in these processes .

How does dysfunction of SLC25A36 impact mitochondrial function and cellular metabolism? [ADVANCED]

Though specific studies on chicken SLC25A36 dysfunction are not detailed in the search results, insights from related research suggest several potential consequences:

• mtDNA depletion: Based on studies of the yeast ortholog RIM2, loss of SLC25A36 function likely leads to mitochondrial DNA depletion, as observed in yeast where RIM2 deletion causes "total loss of mtDNA" .

• Respiratory chain defects: Disruption of mitochondrial nucleotide transport would impair mitochondrial gene expression, potentially compromising respiratory chain complex assembly and function.

• Cellular energy crisis: Defective mitochondrial function would reduce ATP production through oxidative phosphorylation, potentially triggering compensatory metabolic adaptations.

• Pyrimidine metabolism imbalance: Altered nucleotide transport between cytosol and mitochondria would disrupt cellular pyrimidine pools, affecting various nucleotide-dependent processes beyond mitochondria.

• Growth defects: In yeast, RIM2 deficiency causes "lack of growth on non-fermentative carbon sources," indicating the carrier's importance for respiratory metabolism . Similar growth or functional defects might occur in higher organisms with SLC25A36 dysfunction.

These potential consequences highlight the critical importance of mitochondrial nucleotide transport for cellular homeostasis and the likely significant impacts of SLC25A36 dysfunction on multiple cellular processes.

How can SLC25A36 function be studied in cellular models? [BASIC]

Several experimental approaches can be employed to study SLC25A36 function in cellular models:

• Overexpression systems: Transfection of cells with SLC25A36 expression constructs (wild-type or tagged versions) to study localization, interactions, and effects of increased transport activity.

• Gene silencing: Using siRNA or shRNA to reduce SLC25A36 expression and observe the resulting phenotypes related to mitochondrial function and nucleotide metabolism.

• CRISPR/Cas9 gene editing: Creating knockout or knockin cell lines to study complete loss of function or introduce specific mutations.

• Functional complementation: As demonstrated with human SLC25A36, expressing the protein in model organisms lacking the endogenous ortholog (such as RIM2-deficient yeast) can confirm functional conservation and provide a platform for structure-function studies .

• Mitochondrial function assays: Measuring parameters such as mitochondrial membrane potential, respiration rates, ATP production, mtDNA content, and mitochondrial transcription to assess the impact of SLC25A36 modulation.

The search results specifically mention that "the phenotypes of Saccharomyces cerevisiae cells lacking RIM2, the gene encoding the well characterized yeast mitochondrial pyrimidine nucleotide carrier, were overcome by expressing SLC25A33 or SLC25A36 in these cells," demonstrating the utility of yeast complementation studies .

What disease models or phenotypes are associated with SLC25A36 dysfunction? [ADVANCED]

While the search results don't provide specific disease associations for chicken SLC25A36, information about the human ortholog offers some insights:

• OMIM association: Human SLC25A36 is linked to OMIM:616149, suggesting a potential disease association, though specific details are not provided in the search results .

• Mitochondrial disease relevance: Given that other members of the SLC25 family are "responsible for 12 monogenic diseases" , SLC25A36 dysfunction might similarly contribute to mitochondrial disease phenotypes.

• Potential phenotypes: Based on its function, SLC25A36 dysfunction might manifest as:

  • mtDNA depletion syndromes

  • Mitochondrial translation defects

  • Tissues with high energy demands (muscle, brain) most affected

  • Developmental abnormalities due to energy deficiency

• Model organism phenotypes: In mice, the search results indicate there are at least two phenotypic alleles of Slc25a36: one targeted knockout and one gene trap model , suggesting experimental disease models exist but their specific phenotypes aren't detailed in the provided information.

• Yeast model: Loss of the yeast ortholog RIM2 results in complete loss of mitochondrial DNA and inability to grow on non-fermentable carbon sources, indicating the essential nature of this transport function for respiratory metabolism .

These observations suggest that SLC25A36 dysfunction could potentially contribute to human mitochondrial diseases, particularly those involving mtDNA maintenance and expression.

What are the main technical challenges in expressing and studying mitochondrial carrier proteins like SLC25A36? [BASIC]

Studying mitochondrial carrier proteins presents several technical challenges:

• Membrane protein expression: As an integral membrane protein, SLC25A36 can be difficult to express in heterologous systems due to potential toxicity, improper folding, or aggregation.

• Purification difficulties: Extracting membrane proteins while maintaining their native conformation requires careful optimization of detergents and buffer conditions.

• Reconstitution complexities: Creating functional proteoliposomes requires precise control of protein:lipid ratios and reconstitution conditions to ensure proper orientation and activity.

• Mitochondrial targeting: When expressing in eukaryotic systems, ensuring proper mitochondrial targeting and insertion is essential for functional studies.

• Transport assay sensitivity: Developing sensitive and specific assays to measure transport activity, particularly for distinguishing between similar nucleotide substrates.

• Protein stability: Maintaining protein stability during purification and storage, as evidenced by the recommendation to avoid repeated freeze-thaw cycles for the recombinant protein .

These challenges explain why "despite the research efforts of many laboratories, the transport properties and the substrate(s) transported by ∼20 human mitochondrial carriers remain as yet unknown" , highlighting the technical difficulties in characterizing this protein family.

What strategies can overcome the limitations in studying SLC25A36 transport kinetics? [ADVANCED]

Several advanced strategies can address the challenges in studying SLC25A36 transport kinetics:

• Optimized expression systems:

  • Use of specialized E. coli strains designed for membrane protein expression

  • Codon optimization for the expression host

  • Use of fusion partners that enhance folding and membrane insertion

  • Controlled expression using tunable promoters to prevent toxicity

• Advanced purification approaches:

  • Systematic screening of detergents and stabilizing agents

  • Nanodiscs or styrene maleic acid lipid particles (SMALPs) as alternatives to traditional detergent solubilization

  • Affinity purification using well-positioned tags that don't interfere with function

• Innovative functional assays:

  • Development of high-throughput screening methods for transport activity

  • Use of fluorescent nucleotide analogs for real-time monitoring

  • Coupling transport to enzymatic reactions for indirect but sensitive detection

  • Single-molecule techniques to study transport mechanics

• Computational approaches:

  • Molecular dynamics simulations to predict transport mechanisms

  • Machine learning to identify structure-function relationships

  • Homology modeling based on related carriers with known structures

• Alternative model systems:

  • Complementation studies in yeast as demonstrated with human SLC25A36

  • Development of cell-free expression systems optimized for membrane proteins

  • Directed evolution to generate variants with enhanced stability or activity

These approaches can help overcome the inherent difficulties in studying mitochondrial carrier proteins and provide deeper insights into the transport mechanisms and kinetics of SLC25A36.

What are the most promising areas for future research on chicken SLC25A36? [BASIC]

Several promising research directions for chicken SLC25A36 include:

• Tissue-specific expression patterns: Investigating how SLC25A36 expression varies across different chicken tissues and developmental stages, which is not yet well-documented in the search results.

• Regulatory mechanisms: Exploring how SLC25A36 expression and activity are regulated, particularly noting its response to estradiol as mentioned in the gene ontology information .

• Comparative studies: Further characterizing chicken SLC25A36 in comparison to human and other species' orthologs to identify conserved and divergent features.

• Functional significance: Determining the importance of SLC25A36 in chicken-specific physiological processes, particularly in tissues with high mitochondrial content.

• Transport specificity: Confirming the substrate specificity and transport kinetics of chicken SLC25A36, particularly whether it matches the profile of the human ortholog in transporting cytosine and uracil nucleotides .

• Structure-function relationships: Identifying key residues and structural elements that determine substrate specificity and transport mechanism.

These research directions would significantly advance our understanding of SLC25A36 function in chickens and contribute to broader knowledge about mitochondrial nucleotide transport across species.

How might studies of SLC25A36 contribute to understanding broader aspects of mitochondrial biology? [ADVANCED]

Research on SLC25A36 has significant potential to enhance our understanding of several fundamental aspects of mitochondrial biology:

• Nucleotide pool regulation: Elucidating how mitochondria maintain their nucleotide pools separate from but coordinated with cytosolic pools, with SLC25A36 serving as a key regulator of this compartmentalization.

• mtDNA maintenance mechanisms: Providing insights into the supply chains that support mitochondrial genome replication and repair, particularly how nucleotide availability influences these processes.

• Evolutionary adaptations: Comparing SLC25A36 across species could reveal evolutionary adaptations in mitochondrial metabolism, particularly in species with different metabolic demands or environmental adaptations.

• Mitochondrial-nuclear communication: Understanding how SLC25A36-mediated transport contributes to the coordination between nuclear and mitochondrial genomes, potentially revealing new signaling mechanisms.

• Therapeutic targets: Identifying potential intervention points for mitochondrial diseases, as SLC25 family members are already linked to multiple monogenic disorders .

• Metabolic network integration: Clarifying how mitochondrial nucleotide transport integrates with broader cellular metabolic networks, particularly pyrimidine synthesis and salvage pathways.

These contributions would address significant knowledge gaps, as approximately 20 human mitochondrial carriers still have unknown transport properties and substrates despite extensive research efforts , suggesting that complete characterization of SLC25A36 would advance the broader field of mitochondrial transporter biology.

What controls should be included when studying SLC25A36 transport function? [BASIC]

When designing experiments to study SLC25A36 transport function, several essential controls should be included:

• Negative controls:

  • Empty liposomes (without reconstituted protein)

  • Liposomes with reconstituted irrelevant/unrelated protein

  • Heat-inactivated SLC25A36 to confirm transport requires functional protein

• Positive controls:

  • Known mitochondrial nucleotide transporters (if available)

  • Human SLC25A36 ortholog for comparative studies

  • Yeast RIM2 as a functional reference point

• Specificity controls:

  • Non-substrate nucleotides (e.g., adenine nucleotides) which should not be transported

  • Varying nucleotide concentrations to demonstrate saturable kinetics

  • Competition assays with unlabeled substrates

• Inhibition controls:

  • Known inhibitors of mitochondrial carriers, including mercurial compounds

  • Transport measured across a range of temperatures to confirm protein-mediated rather than passive diffusion

• Technical controls:

  • Multiple protein:lipid ratios to optimize reconstitution

  • Various buffer conditions to ensure optimal transport activity

  • Time course measurements to establish linear transport rates

These controls ensure that experimental results can be reliably attributed to SLC25A36-mediated transport and provide a foundation for accurate kinetic and mechanistic characterization.

How can isotope labeling and advanced analytical techniques be applied to trace SLC25A36-mediated nucleotide transport in vivo? [ADVANCED]

Isotope labeling and advanced analytical techniques offer powerful approaches for tracing SLC25A36-mediated nucleotide transport in living systems:

• Stable isotope nucleotide tracing:

  • Synthesize 13C/15N-labeled pyrimidine nucleotides

  • Introduce labeled substrates to cells expressing SLC25A36

  • Isolate mitochondria and measure isotope enrichment in mitochondrial nucleotide pools

  • Track incorporation into mtDNA and RNA to determine functional impact

• Metabolic flux analysis:

  • Combine isotope labeling with computational modeling

  • Determine flux rates through different compartments

  • Compare wild-type with SLC25A36-deficient cells to quantify transport contribution

• SILAC proteomics:

  • Identify adaptive changes in mitochondrial proteome in response to SLC25A36 manipulation

  • Detect altered nucleotide metabolism enzyme abundance

• Live-cell imaging approaches:

  • Develop fluorescent nucleotide analogs that are SLC25A36 substrates

  • Use FRET-based sensors to detect nucleotide concentrations in different compartments

  • Apply super-resolution microscopy to visualize transport at individual mitochondria

• Multi-omics integration:

  • Combine transcriptomics, proteomics, and metabolomics

  • Create comprehensive models of nucleotide transport effects

  • Identify regulatory feedback mechanisms