Structural highlights
Function
[NGAL_HUMAN] Iron-trafficking protein involved in multiple processes such as apoptosis, innate immunity and renal development. Binds iron through association with 2,5-dihydroxybenzoic acid (2,5-DHBA), a siderophore that shares structural similarities with bacterial enterobactin, and delivers or removes iron from the cell, depending on the context. Iron-bound form (holo-24p3) is internalized following binding to the SLC22A17 (24p3R) receptor, leading to release of iron and subsequent increase of intracellular iron concentration. In contrast, association of the iron-free form (apo-24p3) with the SLC22A17 (24p3R) receptor is followed by association with an intracellular siderophore, iron chelation and iron transfer to the extracellular medium, thereby reducing intracellular iron concentration. Involved in apoptosis due to interleukin-3 (IL3) deprivation: iron-loaded form increases intracellular iron concentration without promoting apoptosis, while iron-free form decreases intracellular iron levels, inducing expression of the proapoptotic protein BCL2L11/BIM, resulting in apoptosis. Involved in innate immunity, possibly by sequestrating iron, leading to limit bacterial growth.[1]
Evolutionary Conservation
Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf.
Publication Abstract from PubMed
Human neutrophil gelatinase-associated lipocalin (HNGAL) is a member of the lipocalin family of extracellular proteins that function as transporters of small, hydrophobic molecules. HNGAL, a component of human blood granulocytes, binds bacterially derived formyl peptides that act as chemotactic agents and induce leukocyte granule discharge. HNGAL also forms a complex with the proenzyme form of matrix metalloproteinase-9 (pro-MMP-9, or progelatinase B) via an intermolecular disulphide bridge. This association allows the subsequent formation of ternary and quaternary metalloproteinase/inhibitor complexes that vary greatly in their metalloproteinase activities. The structure and dynamics of apo-HNGAL have been determined by NMR spectroscopy. Simulated annealing calculations yielded a set of 20 convergent structures with an average backbone RMSD from mean coordinate positions of 0. 79(+/-0.13) A over secondary structure elements. The overall rotational correlation time (13.3 ns) derived from15N relaxation data is consistent with a monomeric protein of the size of HNGAL (179 residues) under the experimental conditions (1.4 mM protein, pH 6.0, 24.5 degrees C). The structure features an eight-stranded antiparallel beta-barrel, typical of the lipocalin family. One end of the barrel is open, providing access to the binding site within the barrel cavity, while the other is closed by a short 310-helix. The free cysteine residue required for association with pro-MMP-9 lies in an inter-strand loop at the closed end of the barrel. The structure provides a detailed model of the ligand-binding site and has led to the proposal of a site for pro-MMP-9 association. Dynamic data correlate well with structural features, which has allowed us to investigate a mechanism by which a cell-surface receptor might distinguish between apo and holo-HNGAL through conformational changes at the open end of the barrel.
The solution structure and dynamics of human neutrophil gelatinase-associated lipocalin.,Coles M, Diercks T, Muehlenweg B, Bartsch S, Zolzer V, Tschesche H, Kessler H J Mol Biol. 1999 May 28;289(1):139-57. PMID:10339412[2]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
See Also
References
- ↑ Yang J, Goetz D, Li JY, Wang W, Mori K, Setlik D, Du T, Erdjument-Bromage H, Tempst P, Strong R, Barasch J. An iron delivery pathway mediated by a lipocalin. Mol Cell. 2002 Nov;10(5):1045-56. PMID:12453413
- ↑ Coles M, Diercks T, Muehlenweg B, Bartsch S, Zolzer V, Tschesche H, Kessler H. The solution structure and dynamics of human neutrophil gelatinase-associated lipocalin. J Mol Biol. 1999 May 28;289(1):139-57. PMID:10339412 doi:10.1006/jmbi.1999.2755
