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Cryo-EM structure of trimeric human STEAP1 bound to three Fab120.545 fragmentsCryo-EM structure of trimeric human STEAP1 bound to three Fab120.545 fragments
Structural highlights
Function[STEA1_HUMAN] Metalloreductase that has the ability to reduce both Fe(3+) to Fe(2+) and Cu(2+) to Cu(1+). Uses NAD(+) as acceptor.[UniProtKB:Q9CWR7] Publication Abstract from PubMedSix-transmembrane epithelial antigen of the prostate 1 (STEAP1) is an integral membrane protein that is highly upregulated on the cell surface of several human cancers, making it a promising therapeutic target to manage these diseases. It shares sequence homology with three enzymes (STEAP2-4) that catalyze the NADPH-dependent reduction of iron(III). However, STEAP1 lacks an intracellular NADPH-binding domain and does not exhibit cellular ferric-reductase activity. Thus, both the molecular function of STEAP1 and its role in cancer progression remain elusive. Here, we present a ~3.0 A cryo-EM structure of trimeric human STEAP1 bound to three antigen-binding fragments (Fabs) of the clinically used antibody mAb120.545. The structure disclosed that STEAP1 adopts a reductase-like conformation and interacts with the Fabs through its extracellular helices. Enzymatic assays in human cells revealed that STEAP1 promotes iron(III) reduction when fused to the intracellular NADPH-binding domain of its family member STEAP4, suggesting that STEAP1 functions as a ferric reductase in STEAP hetero-trimers. Our work provides a foundation for deciphering the molecular mechanisms of STEAP1 and may be instrumental in the design of new therapeutic strategies to target STEAP1 in cancer. Cryo-EM structure and potential enzymatic function of human six-transmembrane epithelial antigen of the prostate 1.,Oosterheert W, Gros P J Biol Chem. 2020 May 14. pii: RA120.013690. doi: 10.1074/jbc.RA120.013690. PMID:32409586[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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