DNA polymerase type-B B3 subfamily catalytic domain. Archaeal proteins that are involved in DNA replication are similar to those from eukaryotes. Some members of the archaea also possess multiple family B DNA polymerases (B1, B2 and B3). So far there is no specific function(s) has been assigned for different members of the archaea type B DNA polymerases. Phylogenetic analyses of eubacterial, archaeal, and eukaryotic family B DNA polymerases are support independent gene duplications during the evolution of archaeal and eukaryotic family B DNA polymerases. Structural comparison of the thermostable DNA polymerase type B to its mesostable homolog suggests several adaptations to high temperature such as shorter loops, disulfide bridges, and increasing electrostatic interaction at subdomain interfaces.