title: Crystal structures of a template-independent DNA polymerase: murine terminal deoxynucleotidyltransferase.
abstract: The crystal structure of the catalytic core of murine terminal deoxynucleotidyltransferase (TdT) at 2.35 A resolution reveals a typical DNA polymerase beta-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 beta 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 beta. 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 mu, with which it shares 43% sequence identity.
authors.affiliation: Unité de Biochimie Structurale, URA 2185 du CNRS, Institut Pasteur, 25 rue du Dr Roux, 75015 Paris France. delarue@pasteur.fr
authors.forename: M
authors.initials: M
authors.lastname: Delarue
authors.forename: J B
authors.initials: JB
authors.lastname: Boulé
authors.forename: J
authors.initials: J
authors.lastname: Lescar
authors.forename: N
authors.initials: N
authors.lastname: Expert-Bezançon
authors.forename: N
authors.initials: N
authors.lastname: Jourdan
authors.forename: N
authors.initials: N
authors.lastname: Sukumar
authors.forename: F
authors.initials: F
authors.lastname: Rougeon
authors.forename: C
authors.initials: C
authors.lastname: Papanicolaou
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D003460:Crystallization; D004253:DNA Nucleotidylexotransferase / Q000737:chemistry* / Q000235:genetics; D006801:Humans; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation
chemical_list: D004253:DNA Nucleotidylexotransferase