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Selenium plays important roles in human health and these roles may be exerted through its presence in selenoproteins. Among the 25 selenoproteins in human is selenoprotein K (SelK) whose exact function is still unclear. Here, we investigated the conserved structural features of SelK using bioinformatics as an approach to understand the function and regulation of SelK in mammals. Our data showed that mammalian SelK sequences have more than 90% identity relative to the human SelK. Using RT-PCR assays, we found that SelK is expressed in various rat organs including liver, testes, brain, skeletal muscles, kidneys, spleen, lungs and heart. The selenocysteine (Sec) residue in animal SelK is located three amino acid residues from the C-terminal end of the protein. This Sec residue (U) occurs in a conserved GGUGR sequence in animal SelK. We also found SelK Cys homologues occurring in plants that contain cysteine residues in a conserved CGSCCG sequence at the C-terminal end of the protein. Sequences of SelK in various mammals were found to have disordered region that contains conserved sequences of Src homology 3 (SH3) binding motifs, preceded by a potential serine phosphorylation site at position 58. These SH3 binding motifs may be involved in binding of SelK to protein partners containing SH3 binding domains. In conclusion, the conserved GGUGR sequence in animal SelK may be involved in the role of SelK in redox homeostasis. SelK may be involved in protein-protein interactions through its SH3 binding motifs in mammals and this role may be regulated by phosphorylation of the serine residue at position 58.
Keywords : Bioinformatics, protein - protein interaction ; SECIS element; SelK; SelK Cys homologues; SH3 binding, bioinformatics