title: Structural Basis for a Unique ATP Synthase Core Complex from Nanoarcheaum equitans.
abstract: ATP synthesis is a critical and universal life process carried out by ATP synthases. Whereas eukaryotic and prokaryotic ATP synthases are well characterized, archaeal ATP synthases are relatively poorly understood. The hyperthermophilic archaeal parasite, Nanoarcheaum equitans, lacks several subunits of the ATP synthase and is suspected to be energetically dependent on its host, Ignicoccus hospitalis. This suggests that this ATP synthase might be a rudimentary machine. Here, we report the crystal structures and biophysical studies of the regulatory subunit, NeqB, the apo-NeqAB, and NeqAB in complex with nucleotides, ADP, and adenylyl-imidodiphosphate (non-hydrolysable analog of ATP). NeqB is ∼20 amino acids shorter at its C terminus than its homologs, but this does not impede its binding with NeqA to form the complex. The heterodimeric NeqAB complex assumes a closed, rigid conformation irrespective of nucleotide binding; this differs from its homologs, which require conformational changes for catalytic activity. Thus, although N. equitans possesses an ATP synthase core A3B3 hexameric complex, it might not function as a bona fide ATP synthase.
authors.affiliation: Department of Biological Sciences, National University of Singapore, Singapore 117543, Singapore.
authors.forename: Soumya
authors.initials: S
authors.lastname: Mohanty
authors.affiliation: Department of Biological Sciences, National University of Singapore, Singapore 117543, Singapore.
authors.forename: Chacko
authors.initials: C
authors.lastname: Jobichen
authors.affiliation: Department of Biological Sciences, National University of Singapore, Singapore 117543, Singapore.
authors.forename: Vishnu Priyanka Reddy
authors.initials: VPR
authors.lastname: Chichili
authors.affiliation: the Institute of Biocomputation and Physics of Complex Systems (BIFI), Joint-Unit Institute of Physical Chemistry "Rocasolano (IQFR)-Spanish National Research Council (CSIC)-BIFI, and Department of Biochemistry and Molecular and Cell Biology, University of Zaragoza and Fundacion ARAID, Government of Aragon, 50018 Zaragoza, Spain.
authors.forename: Adrián
authors.initials: A
authors.lastname: Velázquez-Campoy
authors.affiliation: Department of Biological Sciences, National University of Singapore, Singapore 117543, Singapore,; Mechanobiology Institute, National University of Singapore, Singapore 117411, Singapore. Electronic address: dbslowbc@nus.edu.sg.
authors.forename: Boon Chuan
authors.initials: BC
authors.lastname: Low
authors.affiliation: Department of Biological Sciences, National University of Singapore, Singapore 117543, Singapore,; Mechanobiology Institute, National University of Singapore, Singapore 117411, Singapore.
authors.forename: Christopher W V
authors.initials: CWV
authors.lastname: Hogue
authors.affiliation: Department of Biological Sciences, National University of Singapore, Singapore 117543, Singapore,. Electronic address: dbsjayar@nus.edu.sg.
authors.forename: J
authors.initials: J
authors.lastname: Sivaraman
mesh_terms: D025181:ATP Synthetase Complexes / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D019843:Archaeal Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D004789:Enzyme Activation; D006860:Hydrogen Bonding; D008958:Models, Molecular; D008969:Molecular Sequence Data; D046588:Nanoarchaeota / Q000201:enzymology* / Q000235:genetics; D010802:Phylogeny; D011487:Protein Conformation; D020836:Protein Structure, Quaternary; D021122:Protein Subunits; D017386:Sequence Homology, Amino Acid; D055672:Static Electricity; D040681:Structural Homology, Protein
chemical_list: D019843:Archaeal Proteins; D021122:Protein Subunits; D025181:ATP Synthetase Complexes
keywords: ATP synthase; Nanoarchaeum equitans; archaea; catalytic core; crystal structure; evolution; protein complex