Afamin is a novel human vitamin E-binding glycoprotein characterization and in vitro expression |
| |
Authors: | Jerkovic Lidija Voegele Andreas F Chwatal Sabine Kronenberg Florian Radcliffe Catherine M Wormald Mark R Lobentanz Eva M Ezeh Benjie Eller Patricia Dejori Norbert Dieplinger Benjamin Lottspeich Friedrich Sattler Wolfgang Uhr Manfred Mechtler Karl Dwek Raymond A Rudd Pauline M Baier Gottfried Dieplinger Hans |
| |
Affiliation: | Division of Genetic Epidemiology, Department of Medical Genetics, Clinical and Molecular Pharmacology, Innsbruck Medical University, Schoepfstrasse 41, A-6020 Innsbruck, Austria. |
| |
Abstract: | Hydrophobic vitamins are transported in human plasma and extravascular fluids by carrier proteins. No specific protein has been described so far for vitamin E, which plays a crucial role in protecting against oxidative damage and disease. We report here the purification of a 75-kDa glycoprotein with vitamin E-binding properties by stepwise chromatography of lipoprotein-depleted human plasma and monitoring of vitamin E (alpha-tocopherol)-binding activity. Partial sequencing identified this protein as afamin, a previously described member of the albumin gene family with four or five potential N-glycosylation sites. Glycosylation analysis indicated that >90% of the glycans were sialylated biantennary complex structures. The vitamin E-binding properties were confirmed using recombinantly expressed afamin. Qualitative and quantitative analysis of plasma and extravascular fluids revealed an abundant presence of this protein not only in plasma (59.8+/-13.3 microg/mL) but also in extravascular fluids such as follicular (34.4+/-12.7 microg/mL) and cerebrospinal (0.28+/-0.16 microg/mL) fluids, suggesting potential roles for afamin in fertility and neuroprotection. Afamin is partly (13%) bound to plasma lipoproteins. Afamin and vitamin E concentrations significantly correlate in follicular and cerebrospinal fluids but not in plasma. The vitamin E association of afamin in follicular fluid was directly demonstrated by gel filtration chromatography and immunoprecipitation which complements the in vitro findings for purified native and recombinant afamin. |
| |
Keywords: | |
本文献已被 PubMed 等数据库收录! |
|