GO:0015137 citrate transmembrane transporter activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0015137 citrate transmembrane transporter activity describes proteins that move citrate (2-hydroxy-1,2,3-propanetricarboxylate) across biological membranes.
• The term is a molecular_function in the Gene Ontology and is also known by the synonym tricarboxylate transport protein.
• Key gene families include SLC13A1 (Na+-sulfate/citrate cotransporter) and SLC25A1 (mitochondrial citrate carrier), which are structurally and functionally distinct.
• Citrate transport is essential for mitochondrial energy metabolism, cytosolic acetyl-CoA production, and iron uptake in bacteria.
• Dysregulation of citrate transporters has been linked to metabolic disorders, cancer, and bacterial virulence.
• CRISPR knockout, point mutation, knock-in, and overexpression models are powerful tools to dissect the physiological roles of citrate transporters.
Description
Citrate transmembrane transporter activity (GO:0015137) is a molecular function that enables the transfer of citrate, a key intermediate of the tricarboxylic acid (TCA) cycle, across biological membranes. This activity is fundamental for cellular metabolism, as citrate must be shuttled between the cytosol, mitochondria, and other compartments to support energy production, fatty acid synthesis, and signaling. Researchers study this term to understand how cells maintain metabolic homeostasis and how disruptions contribute to disease. The Gene Ontology defines this function as enabling the transfer of citrate from one side of a membrane to the other, with the synonym tricarboxylate transport protein. Proteins with this activity are found in both prokaryotes and eukaryotes, and they often couple citrate transport to the movement of ions such as sodium or protons. In bacteria, citrate transporters are involved in iron uptake and virulence. In humans, mitochondrial citrate carriers are essential for the export of citrate to the cytosol, where it is cleaved to acetyl-CoA for lipid biosynthesis. Given its central role in metabolism, citrate transmembrane transporter activity is a target of intense research, with implications for cancer, metabolic disorders, and infectious diseases.
citrate transmembrane transporter activity At A Glance
| GO ID | GO:0015137 |
|---|---|
| GO term | citrate transmembrane transporter activity |
| Ontology | molecular_function |
| Synonym | tricarboxylate transport protein |
| Definition | Enables the transfer of citrate, 2-hydroxy-1,2,3-propanetricarboxylate, from one side of a membrane to the other. |
| Major function | Transport of citrate across cellular membranes |
| Related transporters | SLC13A1, SLC25A1, bacterial citrate transporters |
| Cellular locations | Mitochondrial inner membrane, plasma membrane, bacterial inner membrane |
What Is GO:0015137?
Citrate transmembrane transporter activity (GO:0015137) is defined as the transfer of citrate, 2-hydroxy-1,2,3-propanetricarboxylate, from one side of a membrane to the other. This activity is carried out by integral membrane proteins that form a pore or undergo conformational changes to shuttle citrate across lipid bilayers. The term is classified under molecular_function in the Gene Ontology and is synonymous with tricarboxylate transport protein. It encompasses both secondary active transporters, such as sodium-coupled citrate transporters, and facilitated diffusion carriers.
Why Is citrate transmembrane transporter activity Important in Cell Biology?
Citrate transmembrane transporter activity is critical for maintaining metabolic flux across cellular compartments. In mitochondria, the citrate carrier exports citrate to the cytosol, where it is converted to acetyl-CoA for fatty acid and cholesterol synthesis. In the plasma membrane, sodium-coupled citrate transporters mediate the uptake of citrate from the bloodstream into cells, influencing energy balance and bone mineralization. In bacteria, citrate transporters are part of iron acquisition systems that are essential for virulence. Dysregulation of these transporters has been implicated in cancer, where altered citrate metabolism supports tumor growth, and in metabolic disorders such as obesity and diabetes. Thus, understanding this activity provides insights into fundamental cell biology and offers potential therapeutic targets.
• Essential for mitochondrial export of citrate for cytosolic acetyl-CoA production.
• Mediates citrate uptake in the kidney and intestine via SLC13A1.
• Involved in bacterial iron uptake and virulence.
• Linked to cancer metabolism and tumor growth.
• Plays a role in bone mineralization and calcium homeostasis.
• Target for metabolic disorders such as diabetes and obesity.
• Required for the TCA cycle intermediate shuttling.
• Potential target for antimicrobial therapy.
• Influences insulin secretion in pancreatic beta cells.
• Modulated by membrane potential and ion gradients.
Mechanism, Genes and Research Methods
Substrate Recognition and Binding
In simple terms: The transporter first grabs citrate from one side of the membrane.
Citrate transporters recognize citrate through specific binding pockets that interact with the three carboxyl groups and the hydroxyl group of citrate. Structural studies of a bacterial Mg2+-citrate-binding protein from an ABC transporter revealed a novel fold that binds citrate with high affinity, providing insights into substrate recognition. In eukaryotic sodium-coupled transporters, the binding of sodium ions is required before citrate can bind, ensuring coupling of ion and substrate fluxes.
Conformational Changes and Translocation
In simple terms: The protein changes shape to move citrate across the membrane.
After binding, the transporter undergoes conformational changes that expose the substrate to the opposite side of the membrane. For the mitochondrial citrate carrier SLC25A1, this involves a rocker-switch mechanism typical of mitochondrial carriers. Patch-clamp studies of mitochondrial membrane biophysics have provided direct electrophysiological evidence for such transport events.
Release and Reset
In simple terms: Citrate is released on the other side, and the transporter resets.
Following translocation, citrate is released into the target compartment, and the transporter returns to its initial conformation. This cycle is driven by ion gradients or membrane potential. In sodium-coupled transporters, the release of citrate is accompanied by the release of sodium ions, completing the transport cycle.
Regulation by Cellular Signals
In simple terms: The activity of citrate transporters can be turned up or down by cellular signals.
Citrate transport activity is regulated by various factors, including substrate availability, ion gradients, and post-translational modifications. In bacteria, gene regulation by transmembrane signaling can control the expression of citrate transporters in response to environmental cues. In eukaryotes, hormonal signals and metabolic status can influence the expression and activity of SLC13A1 and SLC25A1.
Key Genes Involved in GO:0015137 citrate transmembrane transporter activity
The following genes encode proteins with citrate transmembrane transporter activity or are directly involved in its regulation.
| Gene | Major Role | Research Relevance |
|---|---|---|
| SLC13A1 | Sodium-coupled citrate/sulfate transporter in kidney and intestine | Studied for roles in sulfate homeostasis and citrate transport |
| SLC25A1 | Mitochondrial citrate carrier (CIC) | Key for citrate export to cytosol; linked to cancer and metabolic disorders |
| SLC13A2 | Na+-dependent dicarboxylate transporter | Transports citrate and other Krebs cycle intermediates |
| SLC13A3 | Na+-dependent dicarboxylate transporter | Involved in renal citrate reabsorption |
| SLC13A5 | Na+-coupled citrate transporter | Highly expressed in liver; target for metabolic disease |
| SLC25A10 | Mitochondrial dicarboxylate carrier | Transports citrate and other metabolites |
| SLC25A11 | Mitochondrial oxoglutarate carrier | Indirectly affects citrate transport |
| SLC25A12 | Mitochondrial aspartate/glutamate carrier | Part of malate-aspartate shuttle affecting citrate |
| SLC25A13 | Mitochondrial aspartate/glutamate carrier | Defects cause citrin deficiency |
| SLC25A21 | Mitochondrial oxodicarboxylate carrier | Transports citrate-related metabolites |
| SLC25A22 | Mitochondrial glutamate carrier | Indirect role in citrate metabolism |
| SLC25A23 | Mitochondrial phosphate carrier | Affects mitochondrial citrate transport |
| SLC25A24 | Mitochondrial phosphate carrier | Affects mitochondrial citrate transport |
| SLC25A25 | Mitochondrial ATP-Mg/Pi carrier | Indirect role in citrate metabolism |
| SLC25A26 | Mitochondrial S-adenosylmethionine carrier | Indirect role |
| SLC25A27 | Mitochondrial uncoupling protein 4 | Indirect role |
| SLC25A28 | Mitochondrial iron transporter | Indirect role |
How Is citrate transmembrane transporter activity Regulated?
Citrate transmembrane transporter activity is regulated at multiple levels. In bacteria, gene regulation by transmembrane signaling controls the expression of citrate transporters in response to environmental signals. In eukaryotes, the activity of SLC13A1 is regulated by sodium gradients and hormonal factors. The mitochondrial citrate carrier SLC25A1 is regulated by substrate availability and post-translational modifications. Additionally, citrate transport can be modulated by membrane potential and ion concentrations, as shown by patch-clamp studies of mitochondrial membranes.
citrate transmembrane transporter activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| SLC25A1 | Cancer, metabolic disorders | Knockout and overexpression in cancer cell lines |
| SLC13A1 | Sulfate homeostasis, obesity | Knockout mouse models |
| SLC13A5 | Epilepsy, metabolic disease | Point mutation knock-in mice |
| Bacterial citrate transporters | Iron uptake, virulence | Bacterial knockout strains |
| CFTR | Cystic fibrosis | Citrate treatment in cell models |
Cancer Metabolism
Altered citrate transport is a hallmark of cancer metabolism. The mitochondrial citrate carrier SLC25A1 is overexpressed in several cancers, where it supports the export of citrate to the cytosol for de novo lipogenesis, a process essential for tumor growth. Targeting SLC25A1 has been proposed as a therapeutic strategy.
Metabolic Disorders
Mutations in SLC13A1 cause sulfate homeostasis disorders, and polymorphisms are associated with obesity and insulin resistance. SLC25A1 deficiency leads to a rare metabolic disorder characterized by developmental delay and lactic acidosis.
Bacterial Infections
In pathogenic bacteria, citrate transporters are part of iron uptake systems that are critical for virulence. For example, Escherichia coli uses citrate transporters to acquire iron, and their expression is regulated by transmembrane signaling.
Cystic Fibrosis
Citrate has been shown to rescue the function of the ΔF508-CFTR chloride channel, suggesting a role for citrate transport in cystic fibrosis pathophysiology.
From citrate transmembrane transporter activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does SLC25A1 knockout affect cancer cell proliferation? | CRISPR knockout in HeLa or MCF7 cells |
| What is the effect of a point mutation in SLC13A1 on citrate transport? | CRISPR point mutation knock-in in HEK293 cells |
| Can overexpression of SLC25A1 rescue citrate export? | CRISPR overexpression in SLC25A1-null cells |
| How does tagged SLC25A1 localize in mitochondria? | Knock-in of fluorescent tag (e.g., GFP) in SLC25A1 locus |
| Does citrate transport regulate insulin secretion? | Knockout of SLC13A5 in pancreatic beta cells |
| What is the role of bacterial citrate transporters in virulence? | Knockout of citrate transporter genes in E. coli |
How to Study the citrate transmembrane transporter activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Patch-clamp | Ion currents and membrane potential | Mitochondrial membrane biophysics |
| X-ray crystallography | Three-dimensional protein structure | Substrate binding site analysis |
| 13C metabolic flux analysis | Transport rate and metabolic flux | Cancer metabolism studies |
| CRISPR knockout screening | Gene essentiality and resistance | Identifying regulators of citrate transport |
| RNA-seq | Gene expression changes | Transcriptional response to citrate availability |
| Proteomics | Protein abundance and modifications | Post-translational regulation of transporters |
| Live-cell imaging | Subcellular localization and dynamics | Tracking tagged transporters in real time |
| Site-directed mutagenesis | Functional impact of specific residues | Structure-function studies |
Patch-Clamp Electrophysiology
Patch-clamp technique can be used to study mitochondrial membrane biophysics and directly measure ion currents associated with citrate transport. This method provides real-time measurements of transporter activity in isolated membranes.
Structural Biology
X-ray crystallography and cryo-EM have been used to determine the structure of a bacterial Mg2+-citrate-binding protein, revealing the molecular basis of citrate recognition. Such studies inform the design of inhibitors.
Metabolic Flux Analysis
Isotope tracing with 13C-labeled citrate can quantify transport rates and metabolic flux through citrate-dependent pathways. This is often combined with mass spectrometry.
CRISPR Screening
Genome-wide CRISPR knockout screens can identify genes that modulate citrate transport activity or sensitivity to citrate transporter inhibitors. This approach is powerful for discovering novel regulators.
How CRISPR Can Be Used to Study GO:0015137 citrate transmembrane transporter activity
Knockout
CRISPR knockout of citrate transporter genes, such as SLC25A1 or SLC13A1, can abolish transport activity and reveal its role in cellular metabolism and disease. For example, SLC25A1 knockout in cancer cells reduces lipogenesis and inhibits tumor growth.
Point Mutation
Introducing point mutations that mimic human disease variants, such as those in SLC13A1 associated with sulfate homeostasis disorders, allows researchers to study the functional consequences of specific amino acid changes on citrate transport.
Knock-in
Knock-in of a fluorescent tag (e.g., GFP) into the endogenous SLC25A1 locus enables real-time imaging of the transporter's subcellular localization and dynamics. Knock-in of disease-associated mutations can create accurate disease models.
Overexpression
CRISPR-mediated overexpression of citrate transporters, such as SLC13A5, can be used to study the effects of increased citrate uptake on cellular metabolism and insulin secretion.
How EDITGENE Supports citrate transmembrane transporter activity Research
Researchers studying citrate transmembrane transporter activity-related genes often need to determine whether a candidate gene is causally involved in citrate transport, metabolic regulation, or disease. EDITGENE provides a comprehensive suite of CRISPR services to accelerate this research.
Contact EDITGENE today to design your custom CRISPR model for citrate transmembrane transporter activity research.
Related Products
| Product name | Cat.No. | Species | Gene ID | |
|---|---|---|---|---|
| SLC13A2 Knockout HEK293 Cell Line | EDJ-KQ6447 | Human | 9058 | Details Get a Quote |
| SFXN5 Knockout HEK293 Cell Line | EDJ-KQ11285 | Human | 94097 | Details Get a Quote |
| SLC13A3 Knockout HEK293 Cell Line | EDJ-KQ14507 | Human | 64849 | Details Get a Quote |
| SLC13A5 Knockout HEK293 Cell Line | EDJ-KQ15296 | Human | 284111 | Details Get a Quote |
| SLC35G1 Knockout HEK293 Cell Line | EDJ-KQ15334 | Human | 159371 | Details Get a Quote |
| SLC35G1 Knockout A-549 Cell Line | EDJ-KQ46055 | Human | 159371 | Details Get a Quote |
| SLC35G1 Knockout HCT 116 Cell Line | EDJ-KQ46056 | Human | 159371 | Details Get a Quote |
| SLC35G1 Knockout HeLa Cell Line | EDJ-KQ46057 | Human | 159371 | Details Get a Quote |
| SFXN5 Knockout A-549 Cell Line | EDJ-KQ39395 | Human | 94097 | Details Get a Quote |
| SFXN5 Knockout HCT 116 Cell Line | EDJ-KQ39396 | Human | 94097 | Details Get a Quote |
| SFXN5 Knockout HeLa Cell Line | EDJ-KQ39397 | Human | 94097 | Details Get a Quote |
| SLC25A1 Knockout HEK293 Cell Line | EDJ-KQ50635 | Human | 6576 | Details Get a Quote |
| SLC25A1 Knockout HeLa Cell Line | EDJ-KQ54517 | Human | 6576 | Details Get a Quote |
| SLC13A2 Knockout HeLa Cell Line | EDJ-KQ55068 | Human | 9058 | Details Get a Quote |
| SLC13A3 Knockout HeLa Cell Line | EDJ-KQ57087 | Human | 64849 | Details Get a Quote |
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Frequently Asked Questions About citrate transmembrane transporter activity
What is citrate transmembrane transporter activity?
It is a molecular function (GO:0015137) that enables the transfer of citrate across biological membranes.
What genes are involved in citrate transmembrane transporter activity?
Key genes include SLC13A1, SLC25A1, SLC13A5, and bacterial citrate transporters.
What is the synonym for GO:0015137?
The synonym is tricarboxylate transport protein.
How is citrate transported across the mitochondrial membrane?
The mitochondrial citrate carrier SLC25A1 exports citrate from the mitochondrial matrix to the cytosol.
What diseases are associated with citrate transporters?
Cancer, metabolic disorders, and bacterial infections have been linked to altered citrate transport.
Can CRISPR be used to study citrate transporters?
Yes, CRISPR knockout, point mutation, knock-in, and overexpression models are widely used.
What methods measure citrate transport activity?
Patch-clamp, metabolic flux analysis, and structural biology are common approaches.
Is citrate transport important for bacterial virulence?
Yes, citrate transporters are involved in iron uptake, which is critical for virulence in bacteria like E. coli.
What is the role of SLC13A1?
SLC13A1 is a sodium-coupled citrate/sulfate transporter in the kidney and intestine.
How does citrate transport affect cancer metabolism?
Citrate export supports de novo lipogenesis, which is essential for tumor growth.
Conclusion
Citrate transmembrane transporter activity (GO:0015137) is a fundamental molecular function that governs the movement of citrate across membranes, impacting energy metabolism, biosynthesis, and disease. Understanding its mechanisms through CRISPR models and advanced methodologies offers promising avenues for therapeutic intervention in cancer, metabolic disorders, and infections. EDITGENE's specialized services empower researchers to dissect these pathways with precision.
References
- 1. Markovich D. 2014. Na+-sulfate cotransporter SLC13A1.. Pflugers Arch 466(1):131-7 PMID: 24193406
- 2. Braun V et al.. 2006. Gene regulation by transmembrane signaling.. Biometals 19(2):103-13 PMID: 16718597
- 3. Braun V et al.. 2005. Gene regulation by transmembrane signaling.. Biometals 18(5):507-17 PMID: 16333751
- 4. Borkenhagen B et al.. 2022. Recovery of ΔF508-CFTR Function by Citrate.. Nutrients 14(20) PMID: 36296967
- 5. Braun V. 2003. Iron uptake by Escherichia coli.. Front Biosci 8:s1409-21 PMID: 12957834
- 6. Pajor AM. 1999. Sodium-coupled transporters for Krebs cycle intermediates.. Annu Rev Physiol 61:663-82 PMID: 10099705
- 7. Kumari A et al.. 2023. Patch-clamp technique to study mitochondrial membrane biophysics.. J Gen Physiol 155(8) PMID: 37347216
- 8. Mandal SK et al.. 2021. Structural and thermodynamic insights into a novel Mg(2+)-citrate-binding protein from the ABC transporter superfamily.. Acta Crystallogr D Struct Biol 77(Pt 12):1516-1534 PMID: 34866608
