(A) Phylogenetic tree of the galactokinase superfamily. The results of neighbor joining analysis are shown, which fully correspond to the maximum likelihood data. The tree was built with 116 galactokinase superfamily members, all < 90% identical to one another. Forty-seven less-informative proteins have been weeded out afterwards. Thick lines indicate a bootstrap value >75% for the corresponding node. Eukaryotic branches are in blue, eubacterial in green, and archaeal in red lines. Three orphan archaeal-specific families within the superfamily stand out, and may include phosphomevalonate kinases, isopentenyl monophosphate kinases, and, less likely, diphosphomevalonate decarboxylases (see text).(B) Blowup of the central region of the tree in Fig. 3A. Numbers indicate the bootstrap support, out of 1000 replicates, for the deep branches in the tree.