 This shows that the poly(A)-binding protein is specific to poly(A) oligonucleotides and not others.Since the two central β-strands are used for poly(A) oligonucleotide binding, the other face of the protein is free for protein-protein interactions.The PABC domain is approximately 75 amino acids and consists of 4 or 5 α-helices depending on the organism – human PABCs have 5, while yeast has been observed to have 4.