Cocrystal structure of an editing complex of Klenow fragment with DNA.
AUTOR(ES)
Freemont, P S
RESUMO
High-resolution crystal structures of editing complexes of both duplex and single-stranded DNA bound to Escherichia coli DNA polymerase I large fragment (Klenow fragment) show four nucleotides of single-stranded DNA bound to the 3'-5' exonuclease active site and extending toward the polymerase active site. Melting of the duplex DNA by the protein is stabilized by hydrophobic interactions between Phe-473, Leu-361, and His-666 and the last three bases at the 3' terminus. Two divalent metal ions interacting with the phosphodiester to be hydrolyzed are proposed to catalyze the exonuclease reaction by a mechanism that may be related to mechanisms of other enzymes that catalyze phospho-group transfer including RNA enzymes. We suggest that the editing active site competes with the polymerase active site some 30 A away for the newly formed 3' terminus. Since a 3' terminal mismatched base pair favors the melting of duplex DNA, its binding and excision at the editing exonuclease site that binds single-stranded DNA is enhanced.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=282619Documentos Relacionados
- Labelling DNA ends with the Klenow fragment of the E. coli DNA polymerase I: a cautionary note.
- Crystal structure of an antiparallel DNA fragment with Hoogsteen base pairing
- Proofreading DNA: recognition of aberrant DNA termini by the Klenow fragment of DNA polymerase I.
- Nucleolin forms a specific complex with a fragment of the viral (minus) strand of minute virus of mice DNA.
- Some implications of an alternative structure for DNA.