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The hfq of different bacteria include an evolutionarily conserved core consisting of amino acid residues 7–66 and has a C terminal tail which diverges significantly in length and sequence(Frandsen et al., 2011). This C terminal tail is associated with the interaction with some sRnas in the protein(Taylor et al., 2017).

Some studies show that this tail is flexible and have disordered regions which can facilitate intermolecular interactions. This disorder appears to provide a moiety who act like a bridge connecting diverse RNA molecules that could be followed by stable accommodation of the substrate at the distal site at the poliA binding motifs.(Frandsen et al., 2011)

The Sm and Lsm proteins are present in members of the Eukarya, Archaea and Bacteria domains, suggesting that this family may have evolved from a early ancestral (Schumacher et al., 2002; Wilusz & Wilusz, 2005). The Sm proteins contain two conserved regions termed the Sm1 and Sm2 motifs, which are separated by a not conserved region, neither in sequence nor in length, named variable region (Schumacher et al., 2002). There are two structures properties set Hfq apart from the others Sm proteins (Schumacher et al., 2002). First, the bacteria Hfq, unlike others described Sm proteins that usually form a heteroheptameric ring structure, oligomerizes to form a homohexameric structure (Wilusz & Wilusz, 2005). Secondly, Hfq variable region contains only a very short loop, whereas in other Sm proteins variable region consists of a long loop and also the β-strands β3 and β4 are extended to form a longer antiparallel sheet (Schumacher et al., 2002).