Selenocysteine is similar to

Selenocysteine is similar to cysteine. Selenocysteine arises co-translationally during its incorporation into peptides. The UGA anticodon of the unusual tRNA designated tRNAsec normally signals to STOP. The ability of the protein synthesizing apparatus to identify a selenocysteine-specific UGA codon involves the selenocysteine inseion element, a stem-loop structure in the untranslated region of the m-RNA. Selenocysteine-tRNAsec is first charged with serine by the Ligase that charges tRNAsec. Subsequent replacement of the serine oxygen by selenium involves seleno- phosphate formed by Selenophosphate synthetase.Ref: Textbook of medical biochemistry, MN Chatterji, 8th edition, page no: 80