SNAP output for PDB entry 3gv7 [SNAP web server]

PDB-id

3gv7; SNAP-derived features in text and JSON formats; DNAproDB

Class

transferase-DNA

Method

X-ray (2.2 Å)

Summary

Human DNA polymerase iota in complex with t template DNA and incoming dttp

Reference

Kirouac KN, Ling H (2009): "Structural basis of error-prone replication and stalling at a thymine base by human DNA polymerase iota." Embo J., 28, 1644-1654. doi: 10.1038/emboj.2009.122.

Abstract

Human DNA polymerase iota (pol iota) is a unique member of Y-family polymerases, which preferentially misincorporates nucleotides opposite thymines (T) and halts replication at T bases. The structural basis of the high error rates remains elusive. We present three crystal structures of pol complexed with DNA containing a thymine base, paired with correct or incorrect incoming nucleotides. A narrowed active site supports a pyrimidine to pyrimidine mismatch and excludes Watson-Crick base pairing by pol. The template thymine remains in an anti conformation irrespective of incoming nucleotides. Incoming ddATP adopts a syn conformation with reduced base stacking, whereas incorrect dGTP and dTTP maintain anti conformations with normal base stacking. Further stabilization of dGTP by H-bonding with Gln59 of the finger domain explains the preferential T to G mismatch. A template 'U-turn' is stabilized by pol and the methyl group of the thymine template, revealing the structural basis of T stalling. Our structural and domain-swapping experiments indicate that the finger domain is responsible for pol's high error rates on pyrimidines and determines the incorporation specificity.