tokens: This machinery involves a secondary structure , SECIS element , in the selenoprotein encoding mRNA , directing selenocysteine insertion at the position of an opal ( UGA ) codon , normally conferring termination of translation .
folded_tokens: this machinery involve a secondary structure , seci element , in the selenoprotein encoding mrna , direct selenocysteine insertion at the position of a opal ( uga ) codon , normally confer termination of translation .