Lipocalin

Source: Wikipedia, the free encyclopedia.
SCOP2
1hms / SCOPe / SUPFAM
OPM superfamily50
OPM protein1kt6
Available protein structures:
Pfam  structures / ECOD  
PDBRCSB PDB; PDBe; PDBj
PDBsumstructure summary
Lipocalin-like domain
Structure of the Escherichia coli lipocalin.[1]
Identifiers
SymbolLipocalin_2
PfamPF08212
Pfam clanCL0116
InterProIPR013208
Available protein structures:
Pfam  structures / ECOD  
PDBRCSB PDB; PDBe; PDBj
PDBsumstructure summary

The lipocalins are a family of proteins which transport small hydrophobic molecules such as

lipids, and most lipocalins are also able to bind to complexed iron (via siderophores[2] or flavonoids[3]) as well as heme.[4] They share limited regions of sequence homology and a common tertiary structure architecture.[5][6][7][8][9] This is an eight stranded antiparallel beta barrel with a repeated + 1 topology enclosing an internal ligand binding site.[7][8]

These proteins are found in

immune response, pheromone transport, biological prostaglandin synthesis, retinoid binding, and cancer cell interactions.[10]

Function

Immune response

Lipocalin proteins are important key players of nutritional immunity by withholding and sequestering micronutrients.

Th2-deviated immune response, important for allergic sensitization, when applied in their apo-form (with an empty calyx devoid of ligands), whereas the holo-form seemed to exert immune-suppressive properties in vitro.[12]

Pheromone transport

The lipocalin family has been connected with the transport of mammalian

ligands for different biological purposes. Lipocalins have been detected as carrier proteins of important pheromones in the nasal mucus of rodents. Major urinary proteins, a lipocalin subfamily, are found in mouse and rat urine and may act as protein pheromones themselves.[13]

Prostaglandin synthesis

Main article: Prostaglandin

This family of proteins plays a part in the biological system of terminal prostaglandin synthesis.

Retinoid binding

beta-carotene (present in plants) are the two main sources of retinoids in the diet. After intake, they are converted to retinol, successively metabolized, and finally bound to retinol binding proteins (lipocalins) in the blood plasma
.

Cancer cell interactions

Because lipocalins are

tumor protease
inhibitors. This research suggests another possible route of protein-tumor investigations.

Allergens

Some of the proteins in this family are allergens. Allergies are hypersensitivity reactions of the immune system to specific substances called allergens (such as pollen, stings, drugs, or food) that, in most people, result in no symptoms. A nomenclature system has been established for antigens (allergens) that cause IgE-mediated atopic allergies in humans.[14] This nomenclature system is defined by a designation that is composed of the first three letters of the genus; a space; the first letter of the species name; a space and an Arabic number. In the event that two species names have identical designations, they are discriminated from one another by adding one or more letters (as necessary) to each species designation.

The allergens in this family include allergens with the following designations: Bla g 4, Bos d 2, Bos d 5, Can f 1, Can f 2, Fel d 4, Equ c 1 and Equ c 2.[citation needed]

Hormone

LCN2 (Lipocalin 2) acts as bone-derived hormone which crosses the BBB and acts on PVN paraventricular nucleus of hypothalamus in the brain.[citation needed]

Structure

Although lipocalins are a broad family of greatly varied proteins, their three-dimensional structure is a unifying characteristic. Lipocalins have an eight-stranded, antiparallel, symmetrical β-barrel fold, which is, in essence, a beta sheet which has been rolled into a cylindrical shape. Inside this barrel is located a ligand binding site, which plays an important role in the lipocalin classification as a transport protein. If lipocalins are genetically engineered in the attempt to modify their binding properties, they are called anticalins.

Family members

The name "lipocalin" has been proposed

VEGP);[21] and lizard epididymal secretory protein IV (LESP IV).[22]

Human proteins that contain lipocalin domain include:

See also

  • Retinol binding protein

References

  1. S2CID 26737744
    .
  2. PMID 12453412
    .
  3. PMID 29120476
    .
  4. PMID 32601225
    .
  5. ^
    S2CID 12416282
    .
  6. PMID 1608945
    .
  7. ^
    S2CID 21613341
    .
  8. ^
    PMID 7684291
    .
  9. PMID 3238752
    .
  10. PMID 36387895
    .
  11. PMID 35769558
    .
  12. PMID 25117976
    .
  13. S2CID 4398766
    .
  14. ^ [WHO/IUIS Allergen Nomenclature Subcommittee King T.P., Hoffmann D., Loewenstein H., Marsh D.G., Platts-Mills T.A.E., Thomas W. Bull. World Health Organ. 72:797-806(1994)]
  15. PMID 1834059
    .
  16. PMID 3064105
    .
  17. PMID 1707134
    .
  18. PMID 2026162
    .
  19. PMID 8069623
    .
  20. PMID 1723819
    .
  21. PMID 7514123
    .
  22. PMID 8486691
    .

Further reading

External links
This article incorporates text from the public domain Pfam and InterPro: IPR000566
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