The crystal structure of CREG, a secreted glycoprotein involved in cellular growth and differentiation

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Pages1832618331; # of pages: 6
Subject61-GH3P4-1-1-1-1-G-E; analysis; Crystal structure; dimerization; genes; genome; glycosylation; human; pha; protein; proteins
AbstractThe cellular repressor of E1A-stimulated genes (CREG) is a secreted glycoprotein that inhibits proliferation and enhances differentiation of human embryonal carcinoma cells. CREG binds to the cation-independent mannose 6 -phosphate (M6P)/insulin-like growth factor II (IGF2) receptor (IGF2R) (M6P/IGF2R), and this receptor has been shown to be required for CREG-induced growth suppression. To better understand CREG function in cellular growth and differentiation, we solved the 3D crystal structure of this protein to 1.9-A resolution. CREG forms a tight homodimeric complex, and CREG monomers display a beta-barrel fold. The three potential glycosylation sites on CREG map to a confined patch opposite the dimer interface. Thus, dimerization of glycosylated CREG likely presents a bivalent ligand for the M6P/IGF2R. Closely related structural homologs of CREG are FMN-binding split-barrel fold proteins that bind flavin mononucleotide. Our structure shows that the putative flavin mononucleotide-binding pocket in CREG is sterically blocked by a loop and several key bulky residues. A mutant of CREG lacking a part of this loop maintained overall structure and dimerization, as well as M6P/IGF2R binding, but lost the growth suppression activity of WT CREG. Thus, analysis of a structure-based mutant of CREG revealed that binding to M6P/IGF2R, while necessary, is not sufficient for CREG-induced growth suppression. These findings indicate that CREG utilizes a known fold
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AffiliationNRC Biotechnology Research Institute; National Research Council Canada
Peer reviewedNo
NRC number47493
NPARC number3539379
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Record identifier466b44f3-452a-452a-94b8-2ead005760f4
Record created2009-03-01
Record modified2016-05-09
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