Thg1 polymerases contain an additional region of conservation C-terminal to the core palm domain that comprise of 5 helices and two strands [1]. This region has several well-conserved charged residues including a basic residue found towards the end of the first helix of this unit might contribute to the Thg1-specific active site [1]. This C-terminal module of Thg1 is predicted to form a helical bundle that functions equivalently to the fingers of the other nucleic acid polymerases, probably in interacting with the template HtRNA [1].

1: Presence of a classical RRM-fold palm domain in Thg1-type 3'- 5'nucleic acid polymerases and the origin of the GGDEF and CRISPR polymerase domains. Anantharaman V, Iyer LM, Aravind L; Biol Direct. 2010;5:43. PMID:20591188