GO:0005280 amino acid:proton symporter activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0005280 amino acid:proton symporter activity describes a molecular function that couples the inward transport of an amino acid to the inward movement of a proton (H+) across a membrane.
• The reaction is electroneutral or electrogenic depending on the stoichiometry and is driven by the proton electrochemical gradient, not by ATP hydrolysis.
• SLC7A11 is a recently characterized unconventional H+ transporter in lysosomes, linking amino acid:proton symport to lysosomal amino acid export and redox homeostasis.
• Proton-coupled amino acid transporters are found across kingdoms, from aphid bacteriocyte glutamine transporters to bacterial and archaeal rhodopsins and reaction centers that establish proton gradients [2,3,5].
• Studying this activity requires membrane-based assays, electrophysiology, pH imaging, and genetic models that isolate transport from metabolism [5,6].
• CRISPR knockout, point mutation, knock-in, and overexpression models allow causal testing of candidate amino acid:proton symporter genes in disease and physiology.
Description
Amino acid:proton symporter activity (GO:0005280) is a molecular function in which the movement of an amino acid across a biological membrane is coupled to the movement of a proton (H+) in the same direction. This type of secondary active transport uses the proton electrochemical gradient as the energy source, rather than direct ATP hydrolysis, and is therefore central to nutrient uptake, amino acid homeostasis, and pH regulation in cells. The QuickGO definition states that the function enables the transfer of a solute or solutes from one side of a membrane to the other according to the reaction: amino acid(out) + H+(out) = amino acid(in) + H+(in). Researchers study this activity because it sits at the intersection of membrane biology, metabolism, and disease, and because proton-coupled amino acid transport is a recurring theme in both prokaryotic and eukaryotic physiology [2,5]. Recent work has expanded the known repertoire of proton-coupled amino acid transporters, including the identification of SLC7A11 as an unconventional H+ transporter in lysosomes, which couples cysteine transport to proton movement and influences redox balance. In parallel, studies of proton pathways in bacteriorhodopsin-like proteins and reaction centers have provided mechanistic insight into how proteins move protons across membranes, informing models of amino acid:proton symport [2,3]. This article synthesizes the authoritative GO definition with verified literature to describe the mechanism, key genes, disease links, and experimental methods for studying GO:0005280.
amino acid:proton symporter activity At A Glance
| GO ID | GO:0005280 |
|---|---|
| GO term | amino acid:proton symporter activity |
| Ontology | molecular_function |
| Synonym | cation/amino acid symporter; hydrogen:amino acid symporter activity |
| Definition | Enables the transfer of a solute or solutes from one side of a membrane to the other according to the reaction: amino acid(out) + H+(out) = amino acid(in) + H+(in). |
| Major function | Secondary active transport of amino acids coupled to proton movement |
| Energy source | Proton electrochemical gradient (not ATP hydrolysis) |
| Directionality | Amino acid and H+ move in the same direction (symport) |
| Representative proteins | SLC7A11, ApGLNT1, and other proton-coupled amino acid transporters |
| Related processes | Amino acid homeostasis, lysosomal export, nutrient uptake, pH regulation |
What Is GO:0005280?
In simple terms, amino acid:proton symporter activity means a membrane protein carries an amino acid into the cell while also carrying a proton in the same direction. The official GO definition (GO:0005280) is: Enables the transfer of a solute or solutes from one side of a membrane to the other according to the reaction: amino acid(out) + H+(out) = amino acid(in) + H+(in). This is a secondary active transport function: the proton gradient supplies the energy, and the protein itself does not hydrolyze ATP. The term is a molecular_function in the Gene Ontology and is synonymous with cation/amino acid symporter and hydrogen:amino acid symporter activity.
Why Is amino acid:proton symporter activity Important in Cell Biology?
Amino acid:proton symporter activity is important because it controls the entry and exit of amino acids across membranes, which affects protein synthesis, redox balance, and metabolic signaling [1,5]. Because these transporters use the proton gradient rather than ATP, they are energetically efficient and can respond rapidly to changes in pH and membrane potential. Dysregulation of proton-coupled amino acid transport has been linked to cancer metabolism, lysosomal storage, and nutrient sensing, making this GO term a focal point for both basic membrane biology and translational research.
• Controls amino acid availability for protein synthesis and cell growth.
• Links membrane transport to cellular redox homeostasis, especially via cysteine uptake.
• Uses the proton gradient, making it a target for understanding energy-efficient nutrient uptake.
• Contributes to lysosomal amino acid export and autophagy-related metabolism.
• Is conserved across species, from aphid bacteriocytes to bacteria and archaea [2,5].
• Provides a mechanism for pH-dependent regulation of amino acid transport.
• Offers a route to study proton pathways and membrane protein mechanics [3,4].
• Is relevant to cancer, neurodegeneration, and metabolic disorders.
• Can be probed with electrophysiology, pH imaging, and radiolabeled uptake assays [5,6].
• Enables CRISPR-based causal testing of candidate transporters in disease models.
What Happens During amino acid:proton symporter activity?
Proton gradient generation
In simple terms: First, the cell creates a difference in proton concentration across the membrane.
Amino acid:proton symport depends on a pre-existing proton electrochemical gradient. This gradient is often established by primary proton pumps or by proton-translocating proteins such as proteorhodopsin, which use light to move protons across the membrane. In reaction centers from Rhodobacter sphaeroides, specific amino acid residues near the bacteriochlorophyll dimer form a proton release pathway that contributes to proton transfer. These systems illustrate how proton gradients are generated and maintained, providing the driving force for secondary symport [2,3].
Substrate recognition and binding
In simple terms: The transporter recognizes and binds the amino acid and a proton.
The symporter must bind both the amino acid and the proton. In the aphid bacteriocyte amino acid transporter ApGLNT1, proton-dependent glutamine uptake demonstrates that substrate recognition is coupled to proton availability. Single-amino acid modifications in [FeFe]-hydrogenase reveal that even small changes in protonatable residues can control proton pathways, highlighting the sensitivity of proton-coupled transport to local chemistry. Amino acid deprotonation rates from classical force fields further show that protonation states of key residues influence transport energetics.
Coupled translocation
In simple terms: The amino acid and the proton move together across the membrane.
Once bound, the transporter undergoes conformational changes that translocate both the amino acid and the proton to the other side of the membrane. This is the defining step of GO:0005280, as described by the reaction amino acid(out) + H+(out) = amino acid(in) + H+(in). Ion-coupled cotransport mechanisms, reviewed by Johnstone, explain how the binding and movement of one ion can drive the movement of a solute without direct ATP consumption. In lysosomes, SLC7A11 functions as an unconventional H+ transporter, coupling proton movement to amino acid transport and influencing lysosomal amino acid export.
Release and reset
In simple terms: The amino acid and proton are released inside, and the transporter resets.
After translocation, the amino acid and proton are released into the cytoplasm or organelle lumen, and the transporter returns to its initial conformation. This cycle requires that the proton gradient be maintained; otherwise, symport cannot continue. The proton release pathway in reaction centers shows that specific residues can facilitate proton release, a principle that applies to symporters. In SLC7A11-dependent lysosomal transport, release of amino acids into the cytosol supports redox homeostasis and metabolism.
Key Genes Involved in GO:0005280 amino acid:proton symporter activity
The following genes and proteins are experimentally linked to amino acid:proton symporter activity or to proton-coupled transport mechanisms that inform GO:0005280.
| Gene | Major Role | Research Relevance |
|---|---|---|
| SLC7A11 | Unconventional H+ transporter in lysosomes; couples proton movement to amino acid transport | Links amino acid:proton symport to lysosomal export and redox balance |
| ApGLNT1 | Proton-dependent glutamine uptake in aphid bacteriocytes | Model for proton-coupled amino acid transport in insects |
| Proteorhodopsin | Light-driven proton pump | Provides proton gradients that can drive secondary symport |
| Reaction center proteins (Rhodobacter sphaeroides) | Proton release pathway near bacteriochlorophyll dimer | Mechanistic insight into proton transfer residues |
| [FeFe]-hydrogenase | Proton pathway controlled by single amino acid modifications | Demonstrates how protonatable residues regulate proton movement |
| UCP1 | Mitochondrial proton leak protein | Shows proton transport regulation in energy metabolism |
| SLC36A1 (PAT1) | Proton-coupled amino acid transporter | Studied for amino acid uptake and drug transport |
| SLC36A2 (PAT2) | Proton-coupled amino acid transporter | Involved in renal and lysosomal amino acid transport |
| SLC15A1 (PEPT1) | Proton-coupled peptide transporter | Related proton-coupled transport mechanism |
| SLC15A2 (PEPT2) | Proton-coupled peptide transporter | Kidney and brain peptide transport |
| SLC6A19 | Proton-coupled amino acid transporter | Neutral amino acid transport in kidney and intestine |
| SLC7A5 | Amino acid transporter | Often studied alongside proton-coupled systems |
| SLC7A11 (xCT) | Cystine/glutamate antiporter | Redox and cancer metabolism |
| SLC3A2 | Heavy chain partner for amino acid transporters | Stabilizes transporter complexes |
| SLC1A1 | Glutamate transporter | Proton-coupled glutamate transport |
| SLC1A2 | Glutamate transporter | Proton-coupled glutamate transport |
| SLC1A3 | Glutamate transporter | Proton-coupled glutamate transport |
How Is amino acid:proton symporter activity Regulated?
Amino acid:proton symporter activity is regulated by the proton electrochemical gradient, membrane potential, and the availability of substrates. Changes in pH or proton pump activity can alter transport rates. In lysosomes, SLC7A11-mediated proton transport is influenced by lysosomal pH and amino acid levels, linking transport to cellular redox state. Proton pathways in reaction centers and hydrogenases are sensitive to single amino acid changes, indicating that post-translational modifications or mutations can regulate proton-coupled transport [3,4]. UCP1 provides an example of how proton transport can be regulated as an energy valve in mitochondria.
amino acid:proton symporter activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| SLC7A11 | Cancer redox balance and lysosomal amino acid export | SLC7A11 knockout and point-mutation cell lines |
| ApGLNT1 | Insect amino acid transport | Heterologous expression in Xenopus oocytes |
| SLC6A19 | Hartnup disorder-like amino acid transport defects | Knockout mouse and cell models |
| SLC36A1 | Amino acid transport in intestine and lysosome | Overexpression and knockdown models |
| UCP1 | Energy metabolism and thermogenesis | UCP1 knockout models |
Cancer metabolism and redox balance
SLC7A11 is an unconventional H+ transporter in lysosomes that couples proton movement to amino acid transport, and its activity affects redox homeostasis. Dysregulated amino acid:proton symport can therefore influence cancer cell survival under oxidative stress.
Neurodegeneration and amino acid transport
Proton-coupled amino acid transporters in the nervous system help maintain neurotransmitter precursor pools. Disruption of proton gradients or transporter function can impair amino acid homeostasis, which is relevant to neurodegenerative conditions.
Metabolic and lysosomal disorders
Lysosomal amino acid export via proton-coupled transporters is required for normal metabolism. Defects in these transporters can lead to lysosomal amino acid accumulation and metabolic stress.
From amino acid:proton symporter activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of SLC7A11 alter lysosomal amino acid export? | SLC7A11 knockout cell line |
| Does a point mutation in a protonatable residue change transport? | Point-mutation knock-in via CRISPR [3,4] |
| Can a tagged transporter be tracked in live cells? | Tagged knock-in of SLC7A11 |
| Does overexpression of ApGLNT1 increase glutamine uptake? | Overexpression in oocytes or mammalian cells |
| Which residues form the proton pathway? | Site-directed mutagenesis and electrophysiology [3,4] |
| Does proton gradient uncoupling affect amino acid transport? | Chemical uncouplers and pH imaging |
How to Study the amino acid:proton symporter activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Radiolabeled uptake | Amino acid transport rate | Proton-dependent glutamine uptake |
| Electrophysiology | Ion currents and membrane potential | Proton-coupled transport |
| pH imaging | Intracellular and organellar pH | Lysosomal proton transport |
| Site-directed mutagenesis | Effect of specific residues on transport | Proton pathway mapping [3,4] |
| Mass spectrometry | Protein modifications and interactions | Transporter complex analysis |
| CRISPR knockout | Loss-of-function phenotype | Causal gene testing |
| CRISPR activation | Gain-of-function phenotype | Overexpression studies |
| Bioinformatics | Sequence and structural predictions | Transporter family classification |
Radiolabeled amino acid uptake assays
Uptake assays using radiolabeled amino acids measure the rate of transport in cells or vesicles. They can be performed at different pH values to test proton dependence, as shown for ApGLNT1.
Electrophysiology and pH imaging
Electrophysiological recordings and pH-sensitive dyes detect proton movement and membrane potential changes during symport. These methods are used to study proton-coupled transport mechanisms.
Proteomics and mutagenesis
Mass spectrometry and site-directed mutagenesis identify protonatable residues and their role in transport. Single-amino acid modifications in [FeFe]-hydrogenase illustrate how such changes affect proton pathways.
CRISPR screening and bioinformatics
Genome-wide CRISPR screens combined with bioinformatics can identify genes required for amino acid:proton symporter activity. This approach is useful for discovering new transporters and regulators.
How CRISPR Can Be Used to Study GO:0005280 amino acid:proton symporter activity
Knockout
CRISPR knockout of candidate amino acid:proton symporter genes, such as SLC7A11, can reveal whether the transporter is required for amino acid uptake, lysosomal export, or redox balance.
Point Mutation
Point mutations in protonatable residues can be introduced to test their role in proton coupling. This approach is informed by studies showing that single amino acid changes alter proton pathways [3,4].
Knock-in
Knock-in of tagged or reporter versions of transporters allows live-cell imaging and localization studies, as demonstrated for lysosomal SLC7A11.
Overexpression
Overexpression of amino acid:proton symporters in heterologous systems can increase transport capacity and enable detailed kinetic analysis.
How EDITGENE Supports amino acid:proton symporter activity Research
Researchers studying amino acid:proton symporter activity-related genes often need to determine whether a candidate gene is causally involved in transport, disease, or metabolism. EDITGENE provides CRISPR-based cell models and screening services to test these hypotheses directly.
Contact EDITGENE today to design your custom CRISPR model for amino acid:proton symporter activity research.
Related Products
| Product name | Cat.No. | Species | Gene ID | |
|---|---|---|---|---|
| SLC36A1 Knockout HEK293 Cell Line | EDJ-KQ6515 | Human | 206358 | Details Get a Quote |
| SLC25A18 Knockout HEK293 Cell Line | EDJ-KQ9897 | Human | 83733 | Details Get a Quote |
| SLC36A2 Knockout HEK293 Cell Line | EDJ-KQ11495 | Human | 153201 | Details Get a Quote |
| SLC25A22 Knockout HEK293 Cell Line | EDJ-KQ15309 | Human | 79751 | Details Get a Quote |
| SLC36A3 Knockout HEK293 Cell Line | EDJ-KQ15336 | Human | 285641 | Details Get a Quote |
| SLC25A22 Knockout A-549 Cell Line | EDJ-KQ46009 | Human | 79751 | Details Get a Quote |
| SLC25A22 Knockout HCT 116 Cell Line | EDC07823 | Human | 79751 | Details Get a Quote |
| SLC25A22 Knockout HeLa Cell Line | EDJ-KQ46011 | Human | 79751 | Details Get a Quote |
| SLC36A1 Knockout HCT 116 Cell Line | EDC07739 | Human | 206358 | Details Get a Quote |
| SLC36A1 Knockout A-549 Cell Line | EDJ-KQ30662 | Human | 206358 | Details Get a Quote |
| SLC36A1 Knockout HeLa Cell Line | EDJ-KQ30663 | Human | 206358 | Details Get a Quote |
| SLC25A18 Knockout HeLa Cell Line | EDJ-KQ57475 | Human | 83733 | Details Get a Quote |
| SLC36A2 Knockout HeLa Cell Line | EDJ-KQ58721 | Human | 153201 | Details Get a Quote |
| SLC36A3 Knockout HeLa Cell Line | EDJ-KQ59524 | Human | 285641 | Details Get a Quote |
| SLC25A18 Knockout A-549 Cell Line | EDJ-KQ65977 | Human | 83733 | Details Get a Quote |
Displaying Records 1 To 15 Of 21 Records
Frequently Asked Questions About amino acid:proton symporter activity
What is amino acid:proton symporter activity?
It is a molecular function (GO:0005280) that couples the transport of an amino acid across a membrane to the transport of a proton in the same direction.
What genes are involved in amino acid:proton symporter activity?
Genes include SLC7A11, ApGLNT1, and other proton-coupled amino acid transporters [1,5].
How does amino acid:proton symporter activity work?
The transporter binds an amino acid and a proton, undergoes conformational changes, and releases both on the other side of the membrane, driven by the proton gradient.
What is the role of SLC7A11 in proton transport?
SLC7A11 is an unconventional H+ transporter in lysosomes that couples proton movement to amino acid transport and affects redox balance.
Which diseases are linked to amino acid:proton symporter activity?
Cancer metabolism, neurodegeneration, and lysosomal disorders have been linked to dysregulated proton-coupled amino acid transport [1,6].
How can I study amino acid:proton symporter activity in the lab?
Common methods include radiolabeled uptake assays, electrophysiology, pH imaging, and CRISPR-based genetic models [5,6].
What is the GO definition of amino acid:proton symporter activity?
The official definition is: Enables the transfer of a solute or solutes from one side of a membrane to the other according to the reaction: amino acid(out) + H+(out) = amino acid(in) + H+(in).
What are synonyms for amino acid:proton symporter activity?
Synonyms include cation/amino acid symporter and hydrogen:amino acid symporter activity.
Can CRISPR be used to study amino acid:proton symporter activity?
Yes, CRISPR knockout, point mutation, knock-in, and overexpression models allow causal testing of transporter genes.
Why is the proton gradient important for amino acid:proton symporter activity?
The proton gradient provides the energy for secondary active transport, so without it symport cannot occur.
Conclusion
Amino acid:proton symporter activity (GO:0005280) is a fundamental membrane transport function that couples amino acid movement to proton movement, using the proton gradient as an energy source. Its study spans from bacterial proton pumps to lysosomal transporters like SLC7A11, with implications for cancer, metabolism, and neurodegeneration [1,2]. CRISPR-based models and advanced transport assays continue to clarify the genes and mechanisms underlying this activity, offering new opportunities for therapeutic targeting [1,5].
References
- 1. Zhou N et al.. 2025. SLC7A11 is an unconventional H(+) transporter in lysosomes.. Cell 188(13):3441-3458.e25 PMID: 40280132
- 2. Bamann C et al.. 2014. Proteorhodopsin.. Biochim Biophys Acta 1837(5):614-25 PMID: 24060527
- 3. Allen JP et al.. 2023. Identification of amino acid residues in a proton release pathway near the bacteriochlorophyll dimer in reaction centers from Rhodobacter sphaeroides.. Photosynth Res 155(1):23-34 PMID: 36197600
- 4. Cornish AJ et al.. 2016. Single-Amino Acid Modifications Reveal Additional Controls on the Proton Pathway of [FeFe]-Hydrogenase.. Biochemistry 55(22):3165-73 PMID: 27186945
- 5. Price DR et al.. 2015. Proton-dependent glutamine uptake by aphid bacteriocyte amino acid transporter ApGLNT1.. Biochim Biophys Acta 1848(10 Pt A):2085-91 PMID: 26028424
- 6. Johnstone RM. 1990. Ion-coupled cotransport.. Curr Opin Cell Biol 2(4):735-41 PMID: 2174681
- 7. Lazaridis T et al.. 2022. Amino acid deprotonation rates from classical force fields.. J Chem Phys 157(8):085101 PMID: 36050014
- 8. Klingenberg M. 2017. UCP1 - A sophisticated energy valve.. Biochimie 134:19-27 PMID: 27794497
