title: Nucleotide control of interdomain interactions in the conformational reaction cycle of SecA.
abstract: The SecA adenosine triphosphatase (ATPase) mediates extrusion of the amino termini of secreted proteins from the eubacterial cytosol based on cycles of reversible binding to the SecYEG translocon. We have determined the crystal structure of SecA with and without magnesium-adenosine diphosphate bound to the high-affinity ATPase site at 3.0 and 2.7 angstrom resolution, respectively. Candidate sites for preprotein binding are located on a surface containing the SecA epitopes exposed to the periplasm upon binding to SecYEG and are thus positioned to deliver preprotein to SecYEG. Comparisons with structurally related ATPases, including superfamily I and II ATP-dependent helicases, suggest that the interaction geometry of the tandem motor domains in SecA is modulated by nucleotide binding, which is shown by fluorescence anisotropy experiments to reverse an endothermic domain-dissociation reaction hypothesized to gate binding to SecYEG.
authors.affiliation: Department of Biological Sciences, 702A Fairchild Center, MC2434, Columbia University, New York, NY 10027, USA. hunt@sid.bio.columbia.edu
authors.forename: John F
authors.initials: JF
authors.lastname: Hunt
authors.forename: Sevil
authors.initials: S
authors.lastname: Weinkauf
authors.forename: Lisa
authors.initials: L
authors.lastname: Henry
authors.forename: John J
authors.initials: JJ
authors.lastname: Fak
authors.forename: Paul
authors.initials: P
authors.lastname: McNicholas
authors.forename: Donald B
authors.initials: DB
authors.lastname: Oliver
authors.forename: Johann
authors.initials: J
authors.lastname: Deisenhofer
mesh_terms: D000244:Adenosine Diphosphate / Q000737:chemistry / Q000378:metabolism*; D000251:Adenosine Triphosphatases / Q000737:chemistry* / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000737:chemistry / Q000378:metabolism*; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001412:Bacillus subtilis / Q000201:enzymology*; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D003460:Crystallization; D018360:Crystallography, X-Ray; D004265:DNA Helicases / Q000737:chemistry; D004269:DNA, Bacterial / Q000737:chemistry / Q000378:metabolism; D004277:DNA, Single-Stranded / Q000737:chemistry / Q000378:metabolism; D019281:Dimerization; D004926:Escherichia coli; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism*; D039601:Eukaryotic Initiation Factor-4A; D005454:Fluorescence Polarization; D005583:Fourier Analysis; D006860:Hydrogen Bonding; D008024:Ligands; D026901:Membrane Transport Proteins / Q000737:chemistry* / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010448:Peptide Initiation Factors / Q000737:chemistry; D010455:Peptides / Q000737:chemistry; D011485:Protein Binding; D011487:Protein Conformation; D017510:Protein Folding; D011498:Protein Precursors / Q000378:metabolism; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D000069816:SEC Translocation Channels; D000081416:SecA Proteins; D013696:Temperature
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004277:DNA, Single-Stranded; D029968:Escherichia coli Proteins; D008024:Ligands; D026901:Membrane Transport Proteins; D010448:Peptide Initiation Factors; D010455:Peptides; D011498:Protein Precursors; D000069816:SEC Translocation Channels; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D039601:Eukaryotic Initiation Factor-4A; D000251:Adenosine Triphosphatases; D004265:DNA Helicases; D000081416:SecA Proteins