title: Purification, crystallization and preliminary X-ray data of the transcription factor NtcA from the cyanobacterium Anabaena PCC 7120.
abstract: NtcA is a transcription factor that acts as a global nitrogen regulator in cyanobacteria. Cyanobacteria are photosynthetic prokaryotic organisms, some genera of which can fix nitrogen under conditions of nitrogen deprivation. NtcA from Anabaena PCC 7120 is a dimeric protein that consists of 223 amino acids with a molecular weight of 25 kDa per subunit. It belongs to the cAMP receptor-protein (CAP) family and is involved in the regulation of several of the genes acting in the nitrogen-fixation process. Here, the crystallization and preliminary X-ray data of NtcA are described. The crystallization was made possible by an improved purification method, which provides a stable NtcA protein at concentrations suitable for crystallization. The protein was crystallized using the hanging-drop method. Data were collected to 2.5 A resolution using synchrotron radiation and the crystals belonged to space group P4(1)2(1)2 or P4(3)2(1)2, with unit-cell parameters a = 69.23, b = 69.23, c = 162.15 A, alpha = beta = gamma = 90 degrees. The phases necessary to solve the structure of NtcA could not be obtained by molecular replacement based on the CAP structure using various models.
authors.affiliation: Department of Biochemistry, Uppsala University, Biomedical Center, Box 576, SE-751 23 Uppsala, Sweden.
authors.forename: Susanne
authors.initials: S
authors.lastname: Wisén
authors.forename: Tove
authors.initials: T
authors.lastname: Sjögren
authors.forename: Birgit
authors.initials: B
authors.lastname: Olin
authors.forename: Bengt
authors.initials: B
authors.lastname: Mannervik
mesh_terms: D017033:Anabaena / Q000737:chemistry*; D003460:Crystallization; D019281:Dimerization; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D014157:Transcription Factors / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification*
chemical_list: D011994:Recombinant Proteins; D014157:Transcription Factors