Phylogenic tree and multiple sequence alignment of bacteriorhodopsins.

<p>(A) Phylogenic tree of haloarchaeal bacteriorhodopsins. (B) <i>Hs</i>BR (PDB code: 1C3W), <i>Hm</i>BRI, BRII and <i>Hw</i>BR are aligned using ClustalW <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0056363#pone.0056363-Thompson1" target="_blank">[41]</a>. The seven-transmembrane helices are labeled A to G. The proton acceptor residues (Asp) are labeled with circles. The position of <i>Hm</i>BRI/D94N is labeled with a triangle, and the residue Lys bound to retinal by Schiff base interaction is labeled with a star.