8p0z | pdb_00008p0z
AP01-S2.3 - a variant of a redesigned transferrin receptor apical domain
Structural highlights
FunctionTFR1_HUMAN Cellular uptake of iron occurs via receptor-mediated endocytosis of ligand-occupied transferrin receptor into specialized endosomes. Endosomal acidification leads to iron release. The apotransferrin-receptor complex is then recycled to the cell surface with a return to neutral pH and the concomitant loss of affinity of apotransferrin for its receptor. Transferrin receptor is necessary for development of erythrocytes and the nervous system (By similarity). A second ligand, the heditary hemochromatosis protein HFE, competes for binding with transferrin for an overlapping C-terminal binding site.[1] Publication Abstract from PubMedTransferrin receptor 1 (TfR) delivers iron across cellular membranes by shuttling the ion carrier protein transferrin. This ability to deliver large protein ligands inside cells is taken advantage of by pathogens to infiltrate human cells. Notably, the receptor's outermost ectodomain, the apical domain, is used as a point of attachment for several viruses including hemorrhagic arenaviruses. To better understand interactions with the receptor it would be advantageous to probe sequence determinants in the apical domain with viral spike proteins. Here, we carried out affinity maturation of our computationally designed apical domain from human TfR to identify underlying driving forces that lead to better binding. The improved variants were confirmed by in vitro surface plasmon resonance measurements with dissociation constants obtained in the lower nanomolar range. It was found that the strong binding affinities for the optimized variants matched the strength of interactions with the native receptor. The structure of the best variant was determined experimentally indicating that the conformational change in the hairpin binding motif at the protein-protein interface plays a crucial role. The experimental methodology can be straightforwardly applied to other arenavirus or pathogens that use the apical domain. It can further be useful to probe host-virus compatibility or therapeutic strategies based on the transferrin receptor decoys. Affinity Maturated Transferrin Receptor Apical Domain Blocks Machupo Virus Glycoprotein Binding.,Sjostrom DJ, Grill B, Ambrosetti E, Veetil AA, Mohlin C, Teixeira AI, Oberdofer G, Bjelic S J Mol Biol. 2023 Sep 9;435(20):168262. doi: 10.1016/j.jmb.2023.168262. PMID:37678707[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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