Finger domain: Used to bind new nucleotides to the template strand, allowing the copy / daughter strand to be extended. ‘Curl’ in when the DNA strand binds to the polymerase, interacting with the thumb domain. This allows a Mg2+ ion to be coordinated, supporting the catalytic process. A steric gate is found on the finger domain, allowing dNTPs and NTPs to be distinguished, ensuring correct binding.
Thumb domain: Interacts with the finger domain, enabling the catalysis of the nucleotide binding reaction.
Palm domain: Interacts with the template DNA strand, aligning it correctly to allow the new strand to be extended.
These three domains give DNA polymerase the appearance of a right hand.
There is also an exo domain, used to remove nucleotides that have been added incorrectly to the new strand. This error correction mechanism is important in ensuring the fidelity of the DNA polymerase is maintained. In order to transfer the new strand to this site, the double helix must be melted slightly, translocating the primer strand into the exo site and allowing the polymerase to backtrack slightly.