Phylogenetic tree of proteins with the same domain architecture as Ng TraI. The phylogenetic tree was generated from the CLUSTAL W alignment of the full-length proteins. A black box highlights the cluster containing Ng TraI. The different font colors represent proteins with similar predicted amphipathic α helices at the N-terminus proximal region: yellow, orange, red, and navy blue. Black font and white font indicate proteins with unique amphipathic α helices. Ng TraI, black font (white background), contains an N-terminal amphipathic α helix. Azoarcus sp. EbN1 (purple font) contains a predicted N-terminal transmembrane domain in addition to the N-terminus proximal amphipathic α helix. Green font indicates proteins that contain two predicted N-terminus proximal amphipathic α helices. Underlined proteins do not contain predicted amphipathic α helices. H. somnus contains a charged reside on the hydrophobic side, and the Shewanella ANA-3 sequence available is truncated. Orange font indicates proteins that conserve motif I and II of relaxases. *Plasmid-encoded proteins.