GO:0019841 retinol binding: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0019841 retinol binding is a molecular function defined as binding to retinol (vitamin A1), an intermediate in the visual cycle and a regulator of growth and differentiation.
• Key proteins include RBP4, RBP2, and cellular retinol-binding proteins (CRBPs), which transport and metabolize retinol [1,2,3,5].
• Retinol binding is essential for retinoid homeostasis, vision, immune function, and wound healing [3,7].
• Dysregulation of retinol-binding proteins is linked to diseases such as type 2 diabetes, idiopathic intracranial hypertension, and fibrosis [3,6].
• CRISPR-based models (knockout, point mutation, knock-in, overexpression) enable causal studies of retinol-binding genes.
• EDITGENE provides comprehensive CRISPR services and bioinformatics to accelerate retinol binding research.
Description
Retinol binding (GO:0019841) is a molecular function that mediates the interaction of proteins with retinol, also known as vitamin A1. This function is critical for the transport, storage, and metabolism of retinoids, which are essential for vision, growth, and differentiation [1,5]. Retinol-binding proteins such as RBP4 and RBP2 facilitate the solubilization and delivery of retinol in aqueous environments, while cellular retinol-binding proteins (CRBPs) regulate intracellular retinoid levels [1,2,3]. Understanding retinol binding is fundamental to deciphering how vitamin A exerts its pleiotropic effects in health and disease. Research into this function has revealed its involvement in metabolic disorders, neurological conditions, and wound healing, making it a target for therapeutic intervention [3,6,7].
retinol binding At A Glance
| GO ID | GO:0019841 |
|---|---|
| GO term | retinol binding |
| Ontology | molecular_function |
| Synonym | vitamin A1 alcohol binding, vitamin A1 binding |
| Major function | Binding to retinol, facilitating its transport, storage, and metabolism |
| Related proteins | RBP4, RBP2, CRBP1, CRBP2, CRBP3, TTR, STRA6 |
| Disease relevance | Metabolic disorders, neurological conditions, fibrosis, wound healing |
| Research methods | CRISPR knockout, point mutation, knock-in, overexpression, structural biology |
What Is GO:0019841?
According to the Gene Ontology, GO:0019841 retinol binding is the binding to retinol, vitamin A1, 2,6,6-trimethyl-1-(9'-hydroxy-3',7'-dimethylnona-1',3',5',7'-tetraenyl)cyclohex-1-ene, one of the three components that makes up vitamin A. Retinol is an intermediate in the vision cycle and it also plays a role in growth and differentiation. This molecular function is exhibited by proteins that specifically recognize and bind retinol, facilitating its transport, storage, and conversion to active metabolites such as retinoic acid.
Why Is retinol binding Important in Cell Biology?
Retinol binding is essential for vitamin A homeostasis, which impacts vision, immune function, reproduction, and embryonic development [1,5]. Proteins that bind retinol, such as RBP4 and RBP2, are not only transporters but also signaling molecules that influence metabolic and inflammatory pathways [2,3]. Dysregulation of retinol binding has been implicated in a range of pathologies, from insulin resistance to idiopathic intracranial hypertension [3,6]. Therefore, studying this function provides insights into basic biology and offers potential therapeutic targets for multiple diseases.
• Essential for vision: retinol is a precursor to retinal, the chromophore in rhodopsin.
• Regulates growth and differentiation via retinoic acid synthesis.
• Modulates immune function and wound healing.
• Involved in metabolic homeostasis; RBP4 is an adipokine linked to insulin resistance.
• Dysregulation leads to neurological disorders such as idiopathic intracranial hypertension.
• Plays a role in fibrosis and tissue remodeling.
• Target for cancer therapy due to effects on cell proliferation and differentiation.
• CRISPR models enable precise dissection of retinol-binding protein functions.
Molecular Mechanism of retinol binding
Substrate recognition and binding pocket
In simple terms: Proteins that bind retinol have a specially shaped pocket that fits retinol like a lock and key.
Retinol-binding proteins such as RBP4 and CRBPs possess a hydrophobic binding pocket that accommodates the retinol molecule. Structural studies have revealed that RBP4 binds retinol in a deep calyx formed by a beta-barrel domain, with specific residues forming hydrogen bonds and van der Waals interactions. This binding is essential for solubilizing retinol in plasma and protecting it from oxidation.
Transport and delivery
In simple terms: After binding, these proteins carry retinol through the blood or inside cells to where it is needed.
RBP4 is secreted by the liver and transports retinol in the bloodstream as a complex with transthyretin (TTR), preventing renal filtration [3,5]. Cellular retinol-binding proteins (CRBPs) facilitate intracellular retinol uptake and trafficking to enzymes that convert it to retinoic acid. RBP2 (also known as CRBP2) is involved in intestinal absorption of dietary retinoids [1,2].
Regulation of retinol binding
In simple terms: The amount of retinol-binding proteins and their ability to bind retinol can change based on the body's needs.
Retinol binding is regulated at multiple levels. RBP4 secretion is influenced by nutritional status, hormones, and inflammation. CRBP expression is modulated by retinoic acid feedback and peroxisome proliferator-activated receptors (PPARs). Additionally, post-translational modifications and interactions with other proteins can affect binding affinity.
Cofactors and structural requirements
In simple terms: Some helper molecules or structural features are needed for retinol binding to work properly.
The binding of retinol to RBP4 requires a specific conformation stabilized by a disulfide bond and a conserved tryptophan residue. For CRBPs, the binding pocket is lined with hydrophobic residues that exclude water. No enzymatic cofactors are required for the binding itself, but subsequent metabolism requires NAD+ or FAD-dependent enzymes.
Key Genes Involved in GO:0019841 retinol binding
The following genes encode proteins that exhibit retinol binding activity or are directly involved in retinol transport and metabolism.
| Gene | Major Role | Research Relevance |
|---|---|---|
| RBP4 | Plasma retinol transport | Linked to insulin resistance, obesity, and metabolic syndrome |
| RBP2 | Intestinal retinol uptake | Dietary retinoid absorption and chylomicron assembly [1,2] |
| CRBP1 | Intracellular retinol transport | Regulates retinoic acid synthesis and cell differentiation |
| CRBP2 | Intestinal retinol metabolism | Facilitates esterification of retinol for storage |
| CRBP3 | Retinol binding in specific tissues | Expressed in heart and skeletal muscle; function under study |
| TTR | Transports RBP4-retinol complex | Mutations cause amyloidosis; affects retinol delivery |
| STRA6 | Cell surface receptor for RBP4 | Mediates retinol uptake; linked to developmental disorders |
| ALDH1A1 | Retinaldehyde dehydrogenase | Converts retinal to retinoic acid; affects differentiation |
| ALDH1A2 | Retinaldehyde dehydrogenase | Critical for embryonic development |
| ALDH1A3 | Retinaldehyde dehydrogenase | Retinoic acid synthesis in specific tissues |
| CYP26A1 | Retinoic acid hydroxylase | Degrades retinoic acid; regulates retinol signaling |
| LRAT | Lecithin retinol acyltransferase | Esterifies retinol for storage |
| RPE65 | Retinal pigment epithelium isomerase | Essential for vision cycle; mutations cause blindness |
| BCO1 | Beta-carotene oxygenase 1 | Cleaves beta-carotene to retinal |
| BCO2 | Beta-carotene oxygenase 2 | Produces apocarotenoids; affects retinol metabolism |
| PNPLA4 | Retinyl ester hydrolase | Mobilizes retinol from stores |
| DGAT1 | Diacylglycerol acyltransferase | Involved in retinyl ester synthesis |
How Is retinol binding Regulated?
Retinol binding is regulated by nutritional and hormonal signals. RBP4 expression is influenced by glucose and insulin, and its secretion is altered in obesity and type 2 diabetes. Retinoic acid, the active metabolite of retinol, feedback-regulates the expression of CRBPs and enzymes involved in retinoid metabolism. In the intestine, RBP2 levels are modulated by dietary fat and vitamin A status. Additionally, inflammatory cytokines can affect RBP4 levels, linking retinol binding to the acute phase response.
retinol binding and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| RBP4 | Insulin resistance, type 2 diabetes | Knockout mouse, overexpression in adipocytes |
| RBP2 | Impaired intestinal retinoid absorption | Intestinal-specific knockout |
| CRBP1 | Cancer, differentiation disorders | Point mutation knock-in |
| STRA6 | Matthew-Wood syndrome | Knockout and rescue |
| TTR | Amyloidosis, retinol transport defects | Knock-in of mutant TTR |
Metabolic disorders
Elevated circulating RBP4 levels are associated with insulin resistance, obesity, and type 2 diabetes. RBP4 is considered an adipokine that contributes to systemic insulin resistance, and its retinol-binding capacity may influence glucose homeostasis. Studies in animal models have shown that RBP4 knockout or overexpression affects insulin sensitivity, making it a therapeutic target.
Neurological conditions
Retinol and RBP4 are present in cerebrospinal fluid, and alterations in their levels have been implicated in idiopathic intracranial hypertension (IIH). It has been hypothesized that vitamin A dysregulation may contribute to IIH pathogenesis, although the exact mechanism remains unclear. Further research is needed to establish causality.
Wound healing and fibrosis
Vitamin A and its binding proteins play a role in wound healing by promoting epithelialization and collagen synthesis. RBP2 is involved in intestinal retinoid uptake, and its deficiency can impair mucosal healing [2,7]. Dysregulated retinol binding may contribute to fibrotic diseases through altered retinoic acid signaling.
From retinol binding-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does RBP4 loss affect insulin sensitivity? | RBP4 knockout mouse |
| How does a point mutation in CRBP1 alter retinol binding? | CRBP1 point-mutation knock-in |
| Can overexpression of RBP2 enhance intestinal retinol uptake? | Transgenic overexpression in intestinal cells |
| What is the effect of STRA6 knockout on embryonic development? | STRA6 knockout zebrafish or mouse |
| Does tagged RBP4 reveal its interaction partners? | Knock-in of epitope-tagged RBP4 |
| Is RBP4 required for vision? | RBP4 knockout followed by electroretinography |
How to Study the retinol binding Process
| Method | What It Measures | Typical Application |
|---|---|---|
| X-ray crystallography | 3D structure of protein-retinol complex | Determining binding pocket residues |
| Isothermal titration calorimetry | Binding affinity (Kd) | Comparing mutant vs wild-type binding |
| CRISPR knockout screen | Genes affecting retinol sensitivity | Identifying novel regulators |
| RNA-seq | Transcriptional changes | Pathway analysis after RBP4 knockout |
| Proteomics | Protein expression and interactions | Identifying RBP4 binding partners |
| Fluorescence microscopy | Cellular localization of retinol | Tracking retinol uptake in live cells |
| Electroretinography | Retinal function | Assessing vision in knockout models |
Structural biology
X-ray crystallography and cryo-electron microscopy can determine the atomic structure of retinol-binding proteins in complex with retinol, revealing key residues and binding modes. These methods are essential for understanding how mutations affect binding affinity.
Biochemical binding assays
Fluorescence titration, isothermal titration calorimetry (ITC), and radioligand binding assays measure the affinity and kinetics of retinol binding to proteins. These techniques can be used to compare wild-type and mutant proteins.
CRISPR screening
Genome-wide CRISPR knockout screens can identify genes that modulate retinol binding or sensitivity to retinoids. Such screens have uncovered novel regulators of retinoid metabolism and signaling.
Transcriptomics and proteomics
RNA-seq and mass spectrometry-based proteomics can profile changes in gene and protein expression upon modulation of retinol-binding proteins, providing insights into downstream pathways.
How CRISPR Can Be Used to Study GO:0019841 retinol binding
Knockout
CRISPR knockout of retinol-binding genes such as RBP4, RBP2, or CRBP1 allows researchers to study loss-of-function phenotypes in cell lines and animal models. For example, RBP4 knockout mice exhibit altered insulin sensitivity and retinoid levels. Knockout models are essential for determining the physiological roles of these proteins.
Point Mutation
Introducing specific point mutations in retinol-binding genes can mimic human polymorphisms or disrupt key binding residues. For instance, mutating the conserved tryptophan in RBP4 may abolish retinol binding, enabling structure-function studies. Point-mutation knock-in models are valuable for dissecting molecular mechanisms.
Knock-in
Knock-in of tagged versions of retinol-binding proteins (e.g., GFP or HA tags) facilitates imaging and interaction studies. Additionally, knock-in of disease-associated mutations can create accurate models of human disorders. For example, knock-in of mutant TTR can model amyloidosis.
Overexpression
Overexpression of retinol-binding proteins using CRISPR activation or transgenic approaches can reveal gain-of-function effects. Overexpressing RBP4 in adipocytes has been shown to induce insulin resistance. Overexpression models are useful for studying the consequences of elevated retinol binding.
How EDITGENE Supports retinol binding Research
Researchers studying retinol binding-related genes often need to determine whether a candidate gene is causally involved in a specific biological process or disease. EDITGENE provides a comprehensive suite of CRISPR-based services to enable such investigations, from gene knockout to precise point mutations and knock-in models.
Contact EDITGENE today to design your custom CRISPR model for retinol binding research.
Frequently Asked Questions About retinol binding
What is retinol binding?
Retinol binding is a molecular function (GO:0019841) where proteins specifically bind to retinol (vitamin A1), facilitating its transport, storage, and metabolism in the body [1,5].
What genes are involved in retinol binding?
Key genes include RBP4, RBP2, CRBP1, CRBP2, CRBP3, TTR, and STRA6, which encode proteins that bind or transport retinol [1,2,3,5].
What is the function of retinol-binding protein 4 (RBP4)?
RBP4 is the primary plasma transporter of retinol, delivering it from the liver to peripheral tissues. It also acts as an adipokine linked to insulin resistance.
How is retinol binding studied?
Methods include X-ray crystallography, isothermal titration calorimetry, CRISPR knockout screens, RNA-seq, and proteomics.
What diseases are associated with retinol binding?
Dysregulation of retinol binding is linked to type 2 diabetes, idiopathic intracranial hypertension, fibrosis, and impaired wound healing [3,6,7].
Can CRISPR be used to study retinol binding?
Yes, CRISPR knockout, point mutation, knock-in, and overexpression models enable precise functional studies of retinol-binding genes.
What is the difference between RBP4 and RBP2?
RBP4 is a secreted plasma transporter, while RBP2 is an intracellular protein involved in intestinal retinol uptake and metabolism [1,2].
What is the role of retinol in vision?
Retinol is converted to retinal, the chromophore in rhodopsin, which is essential for the visual cycle.
How does retinol binding affect cell differentiation?
Retinol is a precursor to retinoic acid, which regulates gene expression and cell differentiation.
What CRISPR services does EDITGENE offer for retinol binding research?
EDITGENE provides knockout, point mutation, knock-in, overexpression, CRISPR library screening, and bioinformatics services for retinol-binding genes.
Conclusion
Retinol binding (GO:0019841) is a fundamental molecular function that underpins vitamin A biology, with critical roles in vision, metabolism, and development. The proteins that mediate this function, such as RBP4 and CRBPs, are implicated in a variety of human diseases, making them important research targets. Advances in CRISPR technology have enabled precise genetic models to dissect the mechanisms and consequences of retinol binding. EDITGENE offers comprehensive services to support these investigations, from gene editing to bioinformatics, empowering researchers to uncover new insights into retinol binding and its therapeutic potential.
References
- 1. Blaner WS et al.. 2020. Retinol-binding protein 2 (RBP2): biology and pathobiology.. Crit Rev Biochem Mol Biol 55(2):197-218 PMID: 32466661
- 2. Plau J et al.. 2022. Retinol-binding protein 2 (RBP2): More than just dietary retinoid uptake.. Biochim Biophys Acta Mol Cell Biol Lipids 1867(8):159179 PMID: 35533980
- 3. Steinhoff JS et al.. 2022. Retinoid Homeostasis and Beyond: How Retinol Binding Protein 4 Contributes to Health and Disease.. Nutrients 14(6) PMID: 35334893
- 5. Zanotti G et al.. 2004. Plasma retinol-binding protein: structure and interactions with retinol, retinoids, and transthyretin.. Vitam Horm 69:271-95 PMID: 15196886
- 6. Libien J et al.. 2007. Retinol and retinol-binding protein in cerebrospinal fluid: can vitamin A take the "idiopathic" out of idiopathic intracranial hypertension?. J Neuroophthalmol 27(4):253-7 PMID: 18090556
- 7. Polcz ME et al.. 2019. The Role of Vitamin A in Wound Healing.. Nutr Clin Pract 34(5):695-700 PMID: 31389093
