title: Structure of Escherichia coli exonuclease I in complex with thymidine 5'-monophosphate.
abstract: In Escherichia coli, exonuclease I (ExoI) is a monomeric processive 3'-5' exonuclease that degrades single-stranded DNA. The enzyme has been implicated as primarily being involved in repairing frameshift mutations. The structure of the enzyme has previously been determined in a hexagonal space group at 2.4 A resolution. Here, the structure of ExoI in complex with a nucleotide product, thymidine 5'-monophosphate, is described in an orthorhombic space group at 1.5 A resolution. This new high-resolution structure provides some insight into the interactions involved in binding a nucleotide product. The conserved active site contains a unique metal-binding position when compared with orthologous sites in the Klenow fragment, T4 DNA polymerase and dnaQ. This unique difference is proposed to be a consequence of the repositioning of an important histidine, His181, away from the active site.
authors.affiliation: Institute of Molecular Biology, Howard Hughes Medical Institute and Department of Physics, 1229 University of Oregon, Eugene, OR 97403-1229, USA. robert.busam@ki.se
authors.forename: Robert D
authors.initials: RD
authors.lastname: Busam
mesh_terms: D001665:Binding Sites; D018360:Crystallography, X-Ray / Q000379:methods; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism; D005090:Exodeoxyribonucleases / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D013938:Thymidine Monophosphate / Q000737:chemistry* / Q000378:metabolism
chemical_list: D029968:Escherichia coli Proteins; D013938:Thymidine Monophosphate; D005090:Exodeoxyribonucleases; C028450:exodeoxyribonuclease I