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Crystal structures of a template‐independent DNA polymerase: murine terminal deoxynucleotidyltransferase
Author(s) -
Delarue M.,
Boulé J.B.,
Lescar J.,
ExpertBezançon N.,
Jourdan N.,
Sukumar N.,
Rougeon F.,
Papanicolaou C.
Publication year - 2002
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/21.3.427
Subject(s) - biology , dna , dna polymerase , microbiology and biotechnology , polymerase chain reaction , polymerase , genetics , gene
The crystal structure of the catalytic core of murine terminal deoxynucleotidyltransferase (TdT) at 2.35 Å resolution reveals a typical DNA polymerase β‐like fold locked in a closed form. In addition, the structures of two different binary complexes, one with an oligonucleotide primer and the other with an incoming ddATP‐Co 2+ complex, show that the substrates and the two divalent ions in the catalytic site are positioned in TdT in a manner similar to that described for the human DNA polymerase β ternary complex, suggesting a common two metal ions mechanism of nucleotidyl transfer in these two proteins. The inability of TdT to accommodate a template strand can be explained by steric hindrance at the catalytic site caused by a long lariat‐like loop, which is absent in DNA polymerase β. However, displacement of this discriminating loop would be sufficient to unmask a number of evolutionarily conserved residues, which could then interact with a template DNA strand. The present structure can be used to model the recently discovered human polymerase μ, with which it shares 43% sequence identity.