SelP is the only known eukaryotic selenoprotein that contains multiple selenocysteine (Sec) residues, and accounts for more than 50% of the selenium content of rat and human plasma [1]. It is thought to be glycosylated [2]. SelP may have antioxidant properties. It can attach to epithelial cells, and may protect vascular endothelial cells against peroxynitrite toxicity [1]. The high selenium content of SelP suggests that it may be involved in selenium intercellular transport or storage [2]. The promoter structure of bovine SelP suggest that it may be involved in countering heavy metal intoxication, and may also have a developmental function [3]. The N-terminal region of SelP can exist independently of the C terminal region. Zebrafish selenoprotein Pb (Swiss:Q98SV0) lacks the C terminal Sec-rich region, and a protein encoded by the rat SelP gene and lacking this region has also been reported [2]. N-terminal region contains a conserved SecxxCys motif, which is similar to the CysxxCys found in thioredoxins. It is speculated that the N terminal region may adopt a thioredoxin fold and catalyse redox reactions [2]. The N-terminal region also contains a His-rich region, which is thought to mediate heparin binding. Binding to heparan proteoglycans could account for the membrane binding properties of SelP [1]. The function of the bacterial members of this family is uncharacterised.

1: Selenoprotein P: properties, functions, and regulation. Mostert V; Arch Biochem Biophys 2000;376:433-438. PMID:10775431

2: Selenium metabolism in zebrafish: multiplicity of selenoprotein genes and expression of a protein containing 17 selenocysteine residues. Kryukov GV, Gladyshev VN; Genes Cells 2000;5:1049-1060. PMID:11168591

3: Analysis of bovine selenoprotein P-like protein gene and availability of metal responsive element (MRE) located in its promoter. Fujii M, Saijoh K, Kobayashi T, Fujii S, Lee MJ, Sumino K; Gene 1997;199:211-217. PMID:9358058