title: Cloning, expression, purification, crystallization and preliminary X-ray characterization of the full-length single-stranded DNA-binding protein from the hyperthermophilic bacterium Aquifex aeolicus.
abstract: Single-stranded DNA-binding (SSB) proteins stabilize single-stranded DNA, which is exposed by separation of the duplex during DNA replication, recombination and repair. The SSB protein from the hyperthermophile Aquifex aeolicus has been overexpressed in Escherichia coli, purified and characterized and crystals of the full-length protein (147 amino acids; M(r) 17 131.20) have been grown by vapour diffusion from ammonium sulfate pH 7.5 in both the absence and presence of ssDNA [dT(pT)(68)]. All crystals diffract to around 2.9 A resolution and those without bound DNA (native) belong to space group P2(1), with two tetramers in the asymmetric unit and unit-cell parameters a = 80.97, b = 73.40, c = 109.76 A, beta = 95.11 degrees . Crystals containing DNA have unit-cell parameters a = 108.65, b = 108.51, c = 113.24 A and could belong to three closely related space groups (I222, I2(1)2(1)2(1) or I4(1)) with one tetramer in the asymmetric unit. Electrospray mass spectrometry of the crystals confirmed that the protein was intact. Molecular replacement with a truncated E. coli SSB structure has revealed the position of the molecules in the unit cell and refinement of both native and DNA-bound forms is under way.
authors.affiliation: School of Chemistry, West Mains Road, University of Edinburgh, Edinburgh EH9 3JJ, Scotland.
authors.forename: David J
authors.initials: DJ
authors.lastname: Clarke
authors.forename: Christopher G
authors.initials: CG
authors.lastname: Northey
authors.forename: Lynsey A
authors.initials: LA
authors.lastname: Mack
authors.forename: Iain W
authors.initials: IW
authors.lastname: McNae
authors.forename: Dmitriy
authors.initials: D
authors.lastname: Alexeev
authors.forename: Lindsay
authors.initials: L
authors.lastname: Sawyer
authors.forename: Dominic J
authors.initials: DJ
authors.lastname: Campopiano
mesh_terms: D000595:Amino Acid Sequence; D001419:Bacteria / Q000737:chemistry*; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D003001:Cloning, Molecular; D003460:Crystallization; D018360:Crystallography, X-Ray; D004277:DNA, Single-Stranded / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D015870:Gene Expression; D006358:Hot Temperature; D008969:Molecular Sequence Data; D016415:Sequence Alignment; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D001426:Bacterial Proteins; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins