Threonine is one of at least 6 amino acid operons are known to be regulated by attenuation. In each a leader sequence of 150–200 bp is found upstream of the first gene in the operon. This leader sequence can assume two different secondary structures known as the terminator and the anti-terminator structure.
Threonine belongs to a group of amino acids whose expression is governed by attenuation mechanisms. Each of these operons contains a 150–200 bp leader sequence preceding the first gene, which can fold into either the terminator or anti-terminator structure.