title: Functional interaction between MutL and 3'-5' exonuclease X in Escherichia coli.
abstract: Exonuclease X is a 3'-5' distributive exonuclease that functions in DNA recombination and repair. It undergoes multiple rounds of binding, hydrolysis, and release to degrade long substrate molecules and thus is very inefficient. In order to identify a cofactor that elevates the excision activity of ExoX, we screened many proteins involved in repair and recombination. We observed that MutL greatly promoted the exonuclease activity of ExoX, and then verified the interaction between MutL and ExoX using SPR and Far-Western analysis. This promotion is independent of ATP and the DNA-binding activity of MutL. We constructed two deletion mutants to analyze this interaction and its regulation of ExoX activity, and found that this functional interaction with ExoX is mainly due to ionic interactions with the N-terminus of MutL. This adds a new role to MutL and gives a clue to MutL's possible regulation on other DnaQ family exonuclease members.
authors.affiliation: National Laboratory of Biomacromolecules and Proteomics Platform, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: Fang
authors.initials: F
authors.lastname: Cheng
authors.forename: Jian
authors.initials: J
authors.lastname: Hou
authors.forename: Yuan-Yuan
authors.initials: YY
authors.lastname: Chen
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhou
authors.forename: Hong-Tai
authors.initials: HT
authors.lastname: Zhang
authors.forename: Li-Jun
authors.initials: LJ
authors.lastname: Bi
authors.forename: Xian-En
authors.initials: XE
authors.lastname: Zhang
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D001483:Base Sequence; D026481:Blotting, Far-Western; D053903:DNA Breaks, Double-Stranded; D053843:DNA Mismatch Repair; D004269:DNA, Bacterial / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D005092:Exonucleases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D000070956:MutL Proteins; D050505:Mutant Proteins / Q000235:genetics / Q000378:metabolism; D010957:Plasmids / Q000235:genetics; D025941:Protein Interaction Mapping; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D020349:Surface Plasmon Resonance
chemical_list: D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; C074770:MutL protein, E coli; D050505:Mutant Proteins; D011994:Recombinant Proteins; D000255:Adenosine Triphosphate; D005092:Exonucleases; D000251:Adenosine Triphosphatases; D000070956:MutL Proteins