title: Crystal structures of the BsPif1 helicase reveal that a major movement of the 2B SH3 domain is required for DNA unwinding.
abstract: Pif1 helicases are ubiquitous members of the SF1B family and are essential for maintaining genome stability. It was speculated that Pif1-specific motifs may fold in specific structures, conferring distinct activities upon it. Here, we report the crystal structures of the Pif1 helicase from Bacteroides spp with and without adenosine triphosphate (ATP) analog/ssDNA. BsPif1 shares structural similarities with RecD2 and Dda helicases but has specific features in the 1B and 2B domains. The highly conserved Pif1 family specific sequence motif interacts with and constraints a putative pin-loop in domain 1B in a precise conformation. More importantly, we found that the 2B domain which contains a specific extended hairpin undergoes a significant rotation and/or movement upon ATP and DNA binding, which is absolutely required for DNA unwinding. We therefore propose a mechanism for DNA unwinding in which the 2B domain plays a predominant role. The fact that the conformational change regulates Pif1 activity may provide insight into the puzzling observation that Pif1 becomes highly processive during break-induced replication in association with Polδ, while the isolated Pif1 has low processivity.
authors.affiliation: College of Life Sciences, Northwest A&F University, Yangling, Shaanxi 712100, China.
authors.forename: Wei-Fei
authors.initials: WF
authors.lastname: Chen
authors.affiliation: College of Life Sciences, Northwest A&F University, Yangling, Shaanxi 712100, China.
authors.forename: Yang-Xue
authors.initials: YX
authors.lastname: Dai
authors.affiliation: College of Life Sciences, Northwest A&F University, Yangling, Shaanxi 712100, China.
authors.forename: Xiao-Lei
authors.initials: XL
authors.lastname: Duan
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: College of Life Sciences, Northwest A&F University, Yangling, Shaanxi 712100, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Shi
authors.affiliation: National Center for Protein Science Shanghai, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China.
authors.forename: Na
authors.initials: N
authors.lastname: Li
authors.affiliation: Beijing National Laboratory for Condensed Matter Physics and CAS Key Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
authors.forename: Ming
authors.initials: M
authors.lastname: Li
authors.affiliation: Beijing National Laboratory for Condensed Matter Physics and CAS Key Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
authors.forename: Shou-Xing
authors.initials: SX
authors.lastname: Dou
authors.affiliation: Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, 19B Yuquan Road, Shijingshan District, Beijing 100049, China.
authors.forename: Yu-Hui
authors.initials: YH
authors.lastname: Dong
authors.affiliation: Institut de Biochimie et Chimie des Protéines, CNRS UMR 5086, 7 passage du Vercors, 69367 Lyon, France stephane.rety@ibcp.fr.
authors.forename: Stephane
authors.initials: S
authors.lastname: Rety
authors.affiliation: College of Life Sciences, Northwest A&F University, Yangling, Shaanxi 712100, China LBPA, Institut d'Alembert, ENS de Cachan, Université Paris-Saclay, CNRS, 61, avenue du Président Wilson, F-94235 Cachan, France xxi01@ens-cachan.fr.
authors.forename: Xu-Guang
authors.initials: XG
authors.lastname: Xi
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry* / Q000378:metabolism; D020816:Amino Acid Motifs; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001439:Bacteroides / Q000737:chemistry* / Q000201:enzymology; D001665:Binding Sites; D017124:Conserved Sequence; D018360:Crystallography, X-Ray; D004265:DNA Helicases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D004258:DNA Polymerase III / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D004277:DNA, Single-Stranded / Q000737:chemistry* / Q000378:metabolism; D015870:Gene Expression; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D004277:DNA, Single-Stranded; D011994:Recombinant Proteins; D000255:Adenosine Triphosphate; D004258:DNA Polymerase III; D004265:DNA Helicases
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