Selenoprotein P-like protein, similar to selenoprotein P, uses multiple TGAs for incorporation of selenocysteines but not as stop codons. It is also characterized by having a His-Pro-rich domain and a regionally differential expression pattern. Hence, in addition to selenium metabolism, this protein is considered to have a developmental function. In the present study, the structure of the selenoprotein P-like protein gene was analyzed. The gene consisted of five exons, and the 5'-flanking region contained a TATA box, TCF-1-CS, bHLH-CS, gamma-IRE-CS, c-Myb-CS, C/EBP-CS, HNF-5-CS, MRE2-CS, etc. The presence of motifs like TCF-1-CS, c-Myb-CS, etc. supports the suggestion that this protein is involved in cellular maturation. Since the presence of MRE2-CS suggests that this protein is related to the antidote effect of selenium against heavy metal intoxication, the availability of this motif was examined using bovine kidney cell lines, CKT-1 and MDBK. Metallothionein mRNA markedly increased 6 h after administration of 10(-6) M CdCl2 and ZnCl2 in both cell lines. No significant alteration was observed in selenoprotein P-like protein mRNA, whereas its basal expression was high, indicating that this protein is constitutively expressed. Thus, it is still possible that this protein acts as an antidote, even though it is not inducible by heavy metals.