Occurrence of azurin-like proteins across a phylogenetic tree. By homology searches, azurin orthologous were found in a variety of bacterial species members of the gamma- and betaproteobacteria but absent from the other bacterial phyla and the Eukarya. Black and white boxes indicate presence and absence of azurin, respectively. The box with vertical bars indicates the existence of an azurin-like protein (termed Laz) in Neisseria species. Shown on the right are the schematic representations of the conserved core domain presented in azurin-like proteins (COX2 superfamily). The phylogenetic tree was drawn using STRING [26]. SP: signal peptide.
