Uterocalin, a lipocalin provisioning the preattachment equine conceptus: fatty acid and retinol binding properties, and structural characterization

作者：Sabine Suire, FRANCESCA STEWART, Jeremy Beauchamp, Malcolm W. Kennedy · 发表于：Biochemical Journal · 年份：2001 · DOI：10.1042/0264-6021:3560369 · 被引用次数：61 · 研究领域：Reproductive Physiology in Livestock、Reproductive System and Pregnancy、Immune Response and Inflammation

The equine conceptus is surrounded by a fibrous capsule that persists until about day 20 of pregnancy, whereupon the capsule is lost, the conceptus attaches to the endometrium and placentation proceeds. Before attachment, the endometrium secretes in abundance a protein of the lipocalin family, uterocalin. The cessation of secretion coincides with the end of the period during which the conceptus is enclosed in its capsule, suggesting that uterocalin is essential for the support of the embryo before direct contact between maternal and foetal tissues is established. Using recombinant protein and fluorescence-based assays, we show that equine uterocalin binds the fluorescent fatty acids 11-(dansylamino)undecanoic acid, dansyl-D,L-alpha-amino-octanoic acid and cis-parinaric acid, and, by competition, oleic, palmitic, arachidonic, docosahexaenoic, gamma-linolenic, cis-eicosapentaenoic and linoleic acids. Uterocalin also binds all-trans-retinol, the binding site for which is coincident or interactive with that for fatty acids. Molecular modelling and intrinsic fluorescence analysis of the wild-type protein and a Trp-->Glu mutant protein indicated that uterocalin has an unusually solvent-exposed Trp side chain projecting from its large helix directly into solvent. This feature is unusual among lipocalins and might relate to binding to, and uptake by, the trophoblast. Uterocalin therefore has the localization and binding activities for the provisioning of the equine conceptus with lip...