OBJECTIVE: Human selenoprotein P (HSelP) is unique protein that contains 10 
selenocysteines encoded by 10 inframe UGA, which typically function as stop 
codon. The function of HSelP remains unclear, in part due to the inability to 
express it by gene recombinant technique. This study is to investigate 
expression and purification of recombinant HSelP in prokaryotic expression 
system, and its activity to induce apoptosis in vitro.
METHODS: The shorter HSelP isoform was cloned. After the selenocysteine (SeCys) 
at 40th position from N terminus of the HSelP shorter isoform was mutated into 
cysteine by PCR, it was expressed in E. coli. The expressed product was purified 
with DEAE column and identified by Western blot. Subsequently, its function on 
induction of mitochondrial apoptotic activity was studied.
RESULTS: The mutant HSelP shorter isoform expressed in prokaryotic system was 
purified by DEAE column to 90% homogeneity. The purified product, HSelP280m, 
induced the opening of mitochondrial permeability transition pore (PTP) and 
decreased the transmembrane potential in a dose-dependent manner. These events 
could be abolished by PTP specific inhibitors.
CONCLUSION: HSelP280m can induce the opening of mitochondrial PTP, which 
provides a basis for investigating the structure and function of recombinant 
HSelP.