title: A 3'-5' exonuclease activity embedded in the helicase core domain of Candida albicans Pif1 helicase.
abstract: 3'-5' exonucleases are frequently found to be associated to polymerases or helicases domains in the same enzyme or could function as autonomous entities. Here we uncovered that Candida albicans Pif1 (CaPif1) displays a 3'-5' exonuclease activity besides its main helicase activity. These two latter activities appear to reside on the same polypeptide and the new exonuclease activity could be mapped to the helicase core domain. We clearly show that CaPif1 displays exclusively exonuclease activity and unambiguously establish the directionality of the exonuclease activity as the 3'-to-5' polarity. The enzyme appears to follow the two-metal-ion driven hydrolyzing activity exhibited by most of the nucleases, as shown by its dependence of magnesium and also by the identification of aspartic residues. Interestingly, an excellent correlation could be found between the presence of the conserved residues and the exonuclease activity when testing activities on Pif1 enzymes from eight fungal organisms. In contrast to others proteins endowed with the double helicase/exonuclease functionality, CaPif1 differs in the fact that the two activities are embedded in the same helicase domain and not located on separated domains. Our findings may suggest a biochemical basis for mechanistic studies of Pif1 family helicases.
authors.affiliation: College of Life Sciences, Northwest A&F University, Yangling, Shaanxi 712100, China.
authors.forename: Xiao-Bin
authors.initials: XB
authors.lastname: Wei
authors.affiliation: College of Life Sciences, Northwest A&F University, Yangling, Shaanxi 712100, China.
authors.forename: Bo
authors.initials: B
authors.lastname: Zhang
authors.affiliation: LBPA, ENS-Cachan, CNRS, Université Paris-Saclay, 61 Avenue du Président Wilson, 94235 Cachan, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Bazeille
authors.affiliation: College of Life Sciences, Northwest A&F University, Yangling, Shaanxi 712100, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Yu
authors.affiliation: College of Life Sciences, Northwest A&F University, Yangling, Shaanxi 712100, China.
authors.forename: Na-Nv
authors.initials: NN
authors.lastname: Liu
authors.affiliation: LBPA, ENS-Cachan, CNRS, Université Paris-Saclay, 61 Avenue du Président Wilson, 94235 Cachan, France.
authors.forename: Brigitte
authors.initials: B
authors.lastname: René
authors.affiliation: LBPA, ENS-Cachan, CNRS, Université Paris-Saclay, 61 Avenue du Président Wilson, 94235 Cachan, France.
authors.forename: Olivier
authors.initials: O
authors.lastname: Mauffret
authors.affiliation: College of Life Sciences, Northwest A&F University, Yangling, Shaanxi 712100, China.|LBPA, ENS-Cachan, CNRS, Université Paris-Saclay, 61 Avenue du Président Wilson, 94235 Cachan, France.
authors.forename: Xu-Guang
authors.initials: XG
authors.lastname: Xi
mesh_terms: D000595:Amino Acid Sequence; D002176:Candida albicans / Q000737:chemistry / Q000201:enzymology*; D017124:Conserved Sequence; D004265:DNA Helicases / Q000737:chemistry* / Q000378:metabolism*; D005092:Exonucleases / Q000737:chemistry / Q000378:metabolism*; D005656:Fungal Proteins / Q000737:chemistry / Q000378:metabolism; D006868:Hydrolysis; D008274:Magnesium / Q000378:metabolism; D000072417:Protein Domains
chemical_list: D005656:Fungal Proteins; D005092:Exonucleases; D004265:DNA Helicases; D008274:Magnesium