A motif of five consecutive residues and two hydrogen bonds in which: residue(i) is Serine (S) or Threonine (T), the side-chain O of residue(i) is H-bonded to the main-chain NH of residue(i+2) or (i+3) , the main-chain CO group of residue(i) is H-bonded to the main-chain NH of residue(i+3) or (i+4).