title: Two unique membrane-bound AAA proteins from Sulfolobus solfataricus.
abstract: Thermoacidophilic crenarchaea of the genus Sulfolobus contain six AAA (ATPase associated with various cellular activities) proteins, including a proteasome-associated ATPase, a Vps4 (vacuolar protein sorting 4) homologue, and two Cdc48 (cell-division cycle 48)-like proteins. The last two AAA proteins are deeply branching divergent members of this family without close relatives outside the Sulfolobales. Both proteins have two nucleotide-binding domains and, unlike other members of the family, they seem to lack folded N-terminal domains. Instead, they contain N-terminal extensions of approx. 50 residues, which are predicted to be unstructured, except for a single transmembrane helix. We have analysed the two proteins, MBA (membrane-bound AAA) 1 and MBA2, by computational and experimental means. They appear to be monophyletic and to share a common ancestor with the Cdc48 clade. Both are membrane-bound and active as nucleotidases upon heterologous expression in Escherichia coli. They form ring complexes, which are stable after solubilization in a mild detergent and whose formation is dependent on the presence of the N-terminal extensions.
authors.affiliation: Department of Protein Evolution, Max-Planck Institute for Developmental Biology, Spemannstrasse 35, 72076 Tübingen, Germany.
authors.forename: Justyna
authors.initials: J
authors.lastname: Serek-Heuberger
authors.forename: Cédric F V
authors.initials: CF
authors.lastname: Hobel
authors.forename: Stanislaw
authors.initials: S
authors.lastname: Dunin-Horkawicz
authors.forename: Beate
authors.initials: B
authors.lastname: Rockel
authors.forename: Jörg
authors.initials: J
authors.lastname: Martin
authors.forename: Andrei N
authors.initials: AN
authors.lastname: Lupas
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D000595:Amino Acid Sequence; D019843:Archaeal Proteins / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D001669:Biochemical Phenomena; D002462:Cell Membrane / Q000201:enzymology*; D019295:Computational Biology; D020285:Cryoelectron Microscopy; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000737:chemistry / Q000378:metabolism; D048229:Sulfolobus solfataricus / Q000201:enzymology*
chemical_list: D019843:Archaeal Proteins; D050505:Mutant Proteins; D000251:Adenosine Triphosphatases