The crystal structures of apo and cAMP-bound GlxR from Corynebacterium glutamicum reveal structural and dynamic changes upon cAMP binding in CRP/FNR family transcription factors.

The cyclic AMP-dependent transcriptional regulator GlxR from Corynebacterium glutamicum is a member of the super-family of CRP/FNR (cyclic AMP receptor protein/fumarate and nitrate reduction regulator) transcriptional regulators that play central roles in bacterial metabolic regulatory networks. In C. glutamicum, which is widely used for the industrial production of amino acids and serves as a non-pathogenic model organism for members of the Corynebacteriales including Mycobacterium tuberculosis, the GlxR homodimer controls the transcription of a large number of genes involved in carbon metabolism.

Crystal structure of PhnF, a GntR-family transcriptional regulator of phosphate transport in Mycobacterium smegmatis.

Bacterial uptake of phosphate is usually accomplished via high-affinity transporters that are commonly regulated by two-component systems, which are activated when the concentration of phosphate is low. Mycobacterium smegmatis possesses two such transporters, the widely distributed PstSCAB system and PhnDCE, a transporter that in other bacteria mediates the uptake of alternative phosphorus sources. We previously reported that the transcriptional regulator PhnF controls the production of the Phn system, acting as a repressor under high-phosphate conditions.

Co(ll)-detection does not follow Kco(ll) gradient: channelling in Co(ll)-sensing.

The MerR-like transcriptional activator CoaR detects surplus Co(ll) to regulate Co(ll) efflux in a cyanobacterium. This organism also has cytosolic metal-sensors from three further families represented by Zn(ll)-sensors ZiaR and Zur plus Ni(ll)-sensor InrS. Here we discover by competition with Fura-2 that CoaR has KCo(ll) weaker than 7 × 10(-8) M, which is weaker than ZiaR, Zur and InrS (KCo(ll) = 6.

Influence of lipids on the interfacial disposition of respiratory syncytical virus matrix protein.

The propensity of a matrix protein from an enveloped virus of the Mononegavirales family to associate with lipids representative of the viral envelope has been determined using label-free methods, including tensiometry and Brewster angle microscopy on lipid films at the air-water interface and atomic force microscopy on monolayers transferred to OTS-treated silicon wafers. This has enabled factors that influence the disposition of the protein with respect to the lipid interface to be characterized. In the absence of sphingomyelin, respiratory syncytial virus matrix protein penetrates monolayers composed of mixtures of phosphocholines with phosphoethanolamines or cholesterol at the air-water interface.

The active site of a carbohydrate esterase displays divergent catalytic and noncatalytic binding functions.

Multifunctional proteins, which play a critical role in many biological processes, have typically evolved through the recruitment of different domains that have the required functional diversity. Thus the different activities displayed by these proteins are mediated by spatially distinct domains, consistent with the specific chemical requirements of each activity. Indeed, current evolutionary theory argues that the colocalization of diverse activities within an enzyme is likely to be a rare event, because it would compromise the existing activity of the protein.

Surface features of a Mononegavirales matrix protein indicate sites of membrane interaction.

The matrix protein (M) of respiratory syncytial virus (RSV), the prototype viral member of the Pneumovirinae (family Paramyxoviridae, order Mononegavirales), has been crystallized and the structure determined to a resolution of 1.6 A. The structure comprises 2 compact beta-rich domains connected by a relatively unstructured linker region.

The Clostridium cellulolyticum dockerin displays a dual binding mode for its cohesin partner.

The plant cell wall degrading apparatus of anaerobic bacteria includes a large multienzyme complex termed the "cellulosome." The complex assembles through the interaction of enzyme-derived dockerin modules with the multiple cohesin modules of the noncatalytic scaffolding protein. Here we report the crystal structure of the Clostridium cellulolyticum cohesin-dockerin complex in two distinct orientations.

Probing the beta-1,3:1,4 glucanase, CtLic26A, with a thio-oligosaccharide and enzyme variants.

The substrate binding regions of a beta-1,3:1,4 glucanase are revealed through structural analysis with a thio-oligosaccharide and kinetics of enzyme variants.

Interplay between kinetically slow thermal spin-crossover and metastable high-spin state relaxation in an iron(II) complex with similar T1/2 and T(LIESST).

This paper describes the first material to show the well-known light-induced excited spin-state trapping (LIESST) effect, the metastable excited state of which relaxes at a temperature approaching its thermal spin-crossover. Cooling polycrystalline [FeL(2)][BF(4)](2).x H(2)O (L=2,6-bis[3-methylpyrazol-1-yl]pyridine; x=0-1/3) at 1 K min(-1) leads to a cooperative spin transition, taking place in two steps centered at 147 and 105 K, that is only 54 % complete by magnetic susceptibility.

Mannose foraging by Bacteroides thetaiotaomicron: structure and specificity of the beta-mannosidase, BtMan2A.

The human colonic bacterium Bacteroides thetaiotaomicron, which plays an important role in maintaining human health, produces an extensive array of exo-acting glycoside hydrolases (GH), including 32 family GH2 glycoside hydrolases. Although it is likely that these enzymes enable the organism to utilize dietary and host glycans as major nutrient sources, the biochemical properties of these GH2 glycoside hydrolases are currently unclear. Here we report the biochemical properties and crystal structure of the GH2 B.

Photomagnetic properties of iron(II) spin crossover complexes of 2,6-dipyrazolylpyridine and 2,6-dipyrazolylpyrazine ligands.

The photomagnetic properties of the following iron(II) complexes have been investigated: [Fe(L1)2][BF4]2, [Fe(L2)2][BF4]2, [Fe(L2)2][ClO4]2, [Fe(L3)2][BF4]2, [Fe(L3)2][ClO4]2 and [Fe(L4)2][ClO4]2 (L1 = 2,6-di{pyrazol-1-yl}pyridine; L2 = 2,6-di{pyrazol-1-yl}pyrazine; L3 = 2,6-di{pyrazol-1-yl}-4-{hydroxymethyl}pyridine; and L4 = 2,6-di{4-methylpyrazol-1-yl}pyridine). Compounds display a complete thermal spin transition centred between 200-300 K, and undergo the light-induced excited spin state trapping (LIESST) effect at low temperatures. The T(LIESST) relaxation temperature of the photoinduced high-spin state for each compound has been determined.

Family 6 carbohydrate binding modules in beta-agarases display exquisite selectivity for the non-reducing termini of agarose chains.

Carbohydrate recognition is central to the biological and industrial exploitation of plant structural polysaccharides. These insoluble polymers are recalcitrant to microbial degradation, and enzymes that catalyze this process generally contain non-catalytic carbohydrate binding modules (CBMs) that potentiate activity by increasing substrate binding. Agarose, a repeat of the disaccharide 3,6-anhydro-alpha-L-galactose-(1,3)-beta-D-galactopyranose-(1,4), is the dominant matrix polysaccharide in marine algae, yet the role of CBMs in the hydrolysis of this important polymer has not previously been explored.

How family 26 glycoside hydrolases orchestrate catalysis on different polysaccharides: structure and activity of a Clostridium thermocellum lichenase, CtLic26A.

One of the most intriguing features of the 90 glycoside hydrolase families (GHs) is the range of specificities displayed by different members of the same family, whereas the catalytic apparatus and mechanism are often invariant. Family GH26 predominantly comprises beta-1,4 mannanases; however, a bifunctional Clostridium thermocellum GH26 member (hereafter CtLic26A) displays a markedly different specificity. We show that CtLic26A is a lichenase, specific for mixed (Glcbeta1,4Glcbeta1,4Glcbeta1,3)n oligo- and polysaccharides, and displays no activity on manno-configured substrates or beta-1,4-linked homopolymers of glucose or xylose.

A study of the thermal and light induced spin transition in [FeL2](BF4)2 and [FeL2](ClO4)2 L=2,6-di(3-methylpyrazol-1-yl)pyrazine.

The spin crossover compounds [FeL2](BF4)2, L=2,6-di(3-methylpyrazol-1-yl)pyrazine and [FeL2](ClO4)2 have very unusual two stage spin transitions which are initially steep and then become more gradual. A detailed variable temperature single crystal X-ray diffraction study has shown that the course of the spin transition is controlled by an order-disorder transition in the counter anions. The high and low spin states both crystallise in the tetragonal space group I4, the structures of the high and low spin states are presented at 290 and 30 K, respectively.

An X-ray powder diffraction study of the spin-crossover transition and structure of bis(2,6-dipyrazol-1-ylpyrazine)iron(II) perchlorate.

The crystal structure of the iron(II) spin-crossover compound [Fe(C(10)H(8)N(6))(2)](ClO(4))(2) in the high-spin state has been solved from powder X-ray diffraction data using the DASH program and refined using Rietveld refinement. The thermal spin transition has been monitored by following the change in unit-cell parameters with temperature. The title compound has been found to undergo a crystallographic phase change, involving a doubling of the crystallographic a axis, on undergoing the spin transition.

Light induced excited high spin-state trapping in [FeL2](BF4)2 (L = 2,6-di(pyrazol-1-yl)pyridine).

The spin-crossover complex [FeL2](BF4)2 undergoes a LIESST transition at 30 K on irradiation; the structures of the low-spin ground and high-spin metastable states at this temperature are presented.