A schematic PGK phylogenetic tree.

Shown are 175 PGK protein sequences rooted with Glycerate kinase from Neisseria meningitides (Detailed analysis, a complete tree (620 sequences) and alignment are given as Supplementary information). All bacterial sequences (in green) and eukaryotic sequences (blue) have lysine at position 219. None of the archeal sequences (in red) harbors a lysine at 219, with the most abundant amino acids being serine (45/73) and threonine (12/73). Redundancy threshold was increased to 93% to create a minimal set of sequences.