Phylogenetic tree of homoserine kinase proteins (HSK). The phylogenetic tree was reconstructed using the maximum likelihood method implemented in the PhyML program (curated alignment with 99 characters was used). The T. pseudonana protein is marked with an asterisk. Reliability for internal branch was assessed using the aLRT. The number next to species name represents entry code of given protein in a databank. Collapsed branches contain sequences of the same species or genus.