2A peptides are a class of 18–22 aa-long peptides, which can induce ribosomal skipping during translation of a protein in a biological cell. These peptides share a core sequence motif of , and are found in a wide range of viral families. 2A peptides can be introduced artificially to help generate polyproteins from a single ORF, by causing the ribosome to fail at making a peptide bond, and then resume translation.
The members of 2A peptides are named after the virus in which they have been first described. For example, F2A, the first described 2A peptide, is derived from foot-and-mouth disease virus. The name "2A" itself comes from the gene numbering scheme of this virus.
These peptides are also known as "self-cleaving" peptides, which is a known misnomer, because the missing peptide bond is never synthesized by the ribosome, and is thus not cleaved.