4r0b | pdb_00004r0b
Structure of dimeric human glycodelin
Structural highlights
FunctionPAEP_HUMAN This protein is, quantitatively, the main protein synthesized and secreted in the endometrium from mid-luteal phase of the menstrual cycle and during the first semester of pregnancy. Publication Abstract from PubMedHuman glycodelin is an abundant glycoprotein from the lipocalin family and involved in crucial biological processes such as reproduction and immune reaction. In females and males, glycodelin is found in four distinct glycoforms - A, C, F and S - that arise from different N-linked oligosaccharide side chains at amino acid residues Asn28 and Asn63. We have expressed glycodelin (carrying two amino acid substitutions to improve solubility) as a non-glycosylated protein in Escherichia coli via periplasmic secretion and determined its X-ray structure at 2.45 A resolution. Glycodelin reveals a classical lipocalin fold including two disulphide bridges, which is however unusually compact and lacks a pronounced central pocket inside the beta-barrel, in line with its low affinity for hydrophobic ligands. Instead, this lipocalin exhibits a unique homodimeric quaternary structure that appears ideally suited as a scaffold for the presentation of specific glycans. In fact, the four oligosaccharides are presented in close proximity on the same side of the dimer surface, which increases avidity for cellular receptors, e.g. during sperm-egg recognition. A bioinformatic analysis showed that glycodelin orthologs exclusively occur in certain suborders of primates that have a menstrual cycle, suggesting that this lipocalin with its role in fertility only recently emerged during evolution. The dimeric crystal structure of the human fertility lipocalin glycodelin reveals a protein scaffold for the presentation of complex glycans.,Schiefner A, Rodewald F, Neumaier I, Skerra A Biochem J. 2014 Nov 24. PMID:25422905[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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