title: Escherichia coli PII protein: purification, crystallization and oligomeric structure.
abstract: The Escherichia coli signal transduction protein PII, product of the glnB gene, was overproduced and purified. The predicted molecular weight of the protein based on the correct nucleotide sequence is 12,427 and is very close to the value 12,435 obtained by matrix-assisted laser desorption mass spectrometry. Hexagonal crystals of the unuridylylated form of PII with dimensions 0.2 x 0.2 x 0.3 mm were grown and analysed by X-ray diffraction. The crystals belong to space group P6(3) with a = b = 61.6 A, c = 56.3 A and Vm of 2.5 for one subunit in the asymmetric unit. A low-resolution electron density map showed electron density concentrated around a three-fold axis, suggesting the molecule to be a trimer. A sedimentation equilibrium experiment of the meniscus depletion type was used to estimate a molecular weight of 35,000 +/- 1,000 for PII in solution. This result is consistent with the native protein being a homotrimer.
authors.affiliation: Centre for Molecular Structure and Function, Research School of Chemistry, Australian National University, Canberra.
authors.forename: S G
authors.initials: SG
authors.lastname: Vasudevan
authors.forename: C
authors.initials: C
authors.lastname: Gedye
authors.forename: N E
authors.initials: NE
authors.lastname: Dixon
authors.forename: E
authors.initials: E
authors.lastname: Cheah
authors.forename: P D
authors.initials: PD
authors.lastname: Carr
authors.forename: P M
authors.initials: PM
authors.lastname: Suffolk
authors.forename: P D
authors.initials: PD
authors.lastname: Jeffrey
authors.forename: D L
authors.initials: DL
authors.lastname: Ollis
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000302:isolation & purification*; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D002852:Chromatography, Ion Exchange; D003460:Crystallization; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000737:chemistry*; D005809:Genes, Regulator; D046911:Macromolecular Substances; D013058:Mass Spectrometry; D008970:Molecular Weight; D009584:Nitrogen / Q000378:metabolism; D051922:PII Nitrogen Regulatory Proteins; D015398:Signal Transduction
chemical_list: D001426:Bacterial Proteins; D046911:Macromolecular Substances; D051922:PII Nitrogen Regulatory Proteins; C404143:PIID regulatory protein, Bacteria; D009584:Nitrogen