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. 2017 Jan 27;8:14246. doi: 10.1038/ncomms14246

Figure 6. A model for NucS protein emergence and evolution.

Figure 6

The unrooted Tree of Life (available and based on ref. 50) was used to depict the proposed evolutionary history of NucS according to our data. The groups relevant to our model are highlighted. Coloured squares depict the NucS-NT (blue) and NucS-CT (red) terminal regions. This model proposes that NucS has an archaeal origin and emerged as a combination of two independent protein domains with complex evolutionary history. Numbers indicate the steps of the model: Both N-terminal and C-terminal regions likely emerged in the archaeal lineage (1). The CT region was transferred via HGT to very few Eukaryotes and to some Bacteria (main groups with any species having the NucS-CT region are labelled with red circles), where the CT domain combined with other regions outside the context of NucS. In the archaeal lineage, NT and CT regions fused to produce the full NucS (2). NucS expanded in many archaeal groups but was also lost in some others. The full NucS protein was transferred to Bacteria by at least two independent HGT events, one to some Deinoccocus-Thermus species (3) and another to Actinobacteria (4).