3LWL: Structure Of Klenow Fragment Of Taq Polymerase In Complex With An Abasic Site

Citation:
Abstract
Abasic sites represent the most frequent DNA lesions in the genome that have high mutagenic potential and lead to mutations commonly found in human cancers. Although these lesions are devoid of the genetic information, adenine is most efficiently inserted when abasic sites are bypassed by DNA polymerases, a phenomenon termed A-rule. In this study, we present X-ray structures of a DNA polymerase caught while incorporating a nucleotide opposite an abasic site. We found that a functionally important tyrosine side chain directs for nucleotide incorporation rather than DNA. It fills the vacant space of the absent template nucleobase and thereby mimics a pyrimidine nucleobase directing for preferential purine incorporation opposite abasic residues because of enhanced geometric fit to the active site. This amino acid templating mechanism was corroborated by switching to pyrimidine specificity because of mutation of the templating tyrosine into tryptophan. The tyrosine is located in motif B and highly conserved throughout evolution from bacteria to humans indicating a general amino acid templating mechanism for bypass of non-instructive lesions by DNA polymerases at least from this sequence family.
PDB ID: 3LWLDownload
MMDB ID: 81884
PDB Deposition Date: 2010/2/24
Updated in MMDB: 2011/05
Experimental Method:
x-ray diffraction
Resolution: 2.25  Å
Source Organism:
synthetic construct
Similar Structures:
Biological Unit for 3LWL: trimeric; determined by author and by software (PISA)
Molecular Components in 3LWL
Label Count Molecule
Protein (1 molecule)
1
DNA Polymerase I, Thermostable
Molecule annotation
Nucleotides(2 molecules)
1
DNA (5'-d(*gp*ap*cp*cp*ap*cp*gp*gp*cp*gp*cp*(2da))-3')
Molecule annotation
1
DNA (5'-d(*ap*ap*ap*(3dr) P*tp*gp*cp*gp*cp*cp*gp*tp*gp*gp*tp*c)-3')
Molecule annotation
Chemicals (18 molecules)
1
1
2
1
3
5
4
7
5
4
* Click molecule labels to explore molecular sequence information.

Citing MMDB
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