title: Crystallization and preliminary X-ray crystallographic analysis of biodegradative threonine deaminase (TdcB) from Salmonella typhimurium.
abstract: Biodegradative threonine deaminase (TdcB) catalyzes the deamination of L-threonine to alpha-ketobutyrate, the first reaction in the anaerobic breakdown of L-threonine to propionate. Unlike the biosynthetic threonine deaminase, TdcB is insensitive to L-isoleucine and is activated by AMP. Here, the cloning of TdcB (molecular weight 36 kDa) from Salmonella typhimurium with an N-terminal hexahistidine affinity tag and its overexpression in Escherichia coli is reported. TdcB was purified to homogeneity using Ni-NTA affinity column chromatography and crystallized using the hanging-drop vapour-diffusion technique in three different crystal forms. Crystal forms I (unit-cell parameters a = 46.32, b = 55.30, c = 67.24 A, alpha = 103.09, beta = 94.70, gamma = 112.94 degrees) and II (a = 56.68, b = 76.83, c = 78.50 A, alpha = 66.12, beta = 89.16, gamma = 77.08 degrees) belong to space group P1 and contain two and four molecules of TdcB, respectively, in the asymmetric unit. Poorly diffracting form III crystals were obtained in space group C2 and based on the unit-cell volume are most likely to contain one molecule per asymmetric unit. Two complete data sets of resolutions 2.2 A (crystal form I) and 1.7 A (crystal form II) were collected at 100 K using an in-house X-ray source.
authors.affiliation: Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India.
authors.forename: Dhirendra K
authors.initials: DK
authors.lastname: Simanshu
authors.forename: Sagar
authors.initials: S
authors.lastname: Chittori
authors.forename: H S
authors.initials: HS
authors.lastname: Savithri
authors.forename: M R N
authors.initials: MR
authors.lastname: Murthy
mesh_terms: D000693:Anaerobiosis; D003001:Cloning, Molecular; D003460:Crystallization / Q000379:methods; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000378:metabolism; D012486:Salmonella typhimurium / Q000201:enzymology*; D013913:Threonine Dehydratase / Q000737:chemistry* / Q000302:isolation & purification
chemical_list: D013913:Threonine Dehydratase