5n48
From Proteopedia
Structure of Anticalin N9B in complex with extra-domain B of human oncofetal fibronectin
Structural highlights
Disease[FINC_HUMAN] Defects in FN1 are the cause of glomerulopathy with fibronectin deposits type 2 (GFND2) [MIM:601894]; also known as familial glomerular nephritis with fibronectin deposits or fibronectin glomerulopathy. GFND is a genetically heterogeneous autosomal dominant disorder characterized clinically by proteinuria, microscopic hematuria, and hypertension that leads to end-stage renal failure in the second to fifth decade of life.[1] 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.[2] [FINC_HUMAN] Fibronectins bind cell surfaces and various compounds including collagen, fibrin, heparin, DNA, and actin. Fibronectins are involved in cell adhesion, cell motility, opsonization, wound healing, and maintenance of cell shape.[3] [4] [5] [6] Anastellin binds fibronectin and induces fibril formation. This fibronectin polymer, named superfibronectin, exhibits enhanced adhesive properties. Both anastellin and superfibronectin inhibit tumor growth, angiogenesis and metastasis. Anastellin activates p38 MAPK and inhibits lysophospholipid signaling.[7] [8] [9] [10] Publication Abstract from PubMedWe describe the comparative X-ray structural analysis of three Anticalin proteins directed against the extra-domain B (ED-B) of oncofetal fibronectin (Fn), a validated marker of tumor neoangiogenesis. The Anticalins were engineered from the human lipocalin 2 (Lcn2) scaffold via targeted randomization of the structurally variable loop region and selection by phage display, resulting in 15-19 exchanged residues. While the four reshaped loops exhibit diverse conformations (with shifts in Calpha positions up to 20.4 A), the beta-barrel core of the lipocalin remains strongly conserved, thus confirming the extraordinary robustness of this scaffold. All three Anticalins bind the cc' hairpin loop of ED-B, the most exposed motif in the context of its neighboring Fn domains, but reveal entirely different binding modes, with orientations differing by up to 180 degrees . Hence, each Anticalin recognizes its molecular target in an individual manner, in line with the distinct epitope specificities previously seen in binding experiments. Anticalins Reveal High Plasticity in the Mode of Complex Formation with a Common Tumor Antigen.,Schiefner A, Gebauer M, Richter A, Skerra A Structure. 2018 Mar 5. pii: S0969-2126(18)30043-1. doi:, 10.1016/j.str.2018.02.003. PMID:29526433[11] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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