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[[sigma].sup.B], a homolog of stress-responsive [[sigma].sup.B] of Bacillus subtilis, controls both osmoprotection and differentiation in Streptomyces coelicolor A3 (2). Its gene is preceded by rsbA and rsbB genes encoding homologs of an anti-sigma factor, RsbW, and its antagonist, RsbV, of B. subtilis, respectively. Purified RsbA bound to [[sigma].sup.B] and prevented [[sigma].sup.B]-directed transcription from the sigBp1 promoter in vitro. An rsbA-null mutant exhibited contrasting behavior to the sigB mutant, with elevated sigBp1 transcription, no actinorhodin production, and precocious aerial mycelial formation, reflecting enhanced activity of [[sigma].sup.B] in vivo. Despite sequence similarity to RsbV, RsbB lacks the conserved phosphorylatable serine residue and its gene disruption produced no distinct phenotype. RsbV (SCO7325) from a putative six-gene operon (rsbV-rsbR-rsbS-rsbT-rsbU1-rsbU) was strongly induced by osmotic stress in a erR-dependent manner. It antagonized the inhibitory action of RsbA on [[sigma].sup.B]-directed transcription and was phosphorylated by RsbA in vitro. These results support the hypothesis that the rapid induction of [[sigma].sup.B] target genes by osmotic stress results from modulation of [[sigma].sup.B] activity by the kinase-anti-sigma factor RsbA and its phosphorylatable antagonist RsbV, which function by a partner-switching mechanism. Amplified induction could result from a rapid increase in the synthesis of both [[sigma].sup.B] and its inhibitor antagonist.

Paraquat (methyl viologen)-resistant mutants of Streptomyces coelicolor A3(2) that grew and sporulated normally in the presence of paraquat were isolated. Based on the positions of the mutant loci in the genetic map, we isolated the pqr (paraquat resistance) gene whose mutation (pqr501) caused a dominant paraquat-resistant phenotype. The pqr locus consists of two genes (pqrA and pqrB) that form a transcription unit. The pqrA gene encodes a protein with a TetR-like DNA-binding motif, and the pqrB gene encodes a putative efflux pump of the major facilitator superfamily. The pqr501 mutation was a base substitution changing arginine-18 to glutamine (R18Q) near the helix-turn-helix motif in PqrA. A pqrA null mutant exhibited similar paraquat resistance, and an increase in the amount of pqrA promoter-driven transcripts of about eightfold was observed for the pqrA501 mutant. These results suggest that PqrA is a negative regulator of its own operon. Deletion of the pqrAB operon caused cells to be very sensitive to paraquat, consistent with the prediction that PqrB may function as a paraquat-efllux pump. Purified PqrA protein specifically bound to the pqrA promoter region, whereas mutant R18Q protein did not, indicating that PqrA is a direct autoregulator of its own operon.

Abstract: Based on the TiO2 nanotube (TONT) with three different thicknesses (10, 18, 28μm) prepared by electrochemical anodization, a double layered electrode consisting of TONT and TiO2 nanoparticles (TONPs) with a size of approximately 20nm was developed. The anodic TONT electrode has been actively investigated due to its beneficial properties such as a favorable electron transport rate and light scattering ability. However, the small specific surface area caused by the large pores and vacant space between 1-D NTs impedes the fabrication of high efficient DSSCs. Hence, the TONP layer with a thickness of 10μm is additionally deposited on the top surface of the TONT film to offer a sufficient surface area for large dye loading. Compared to a single TONT electrode, the double layered TONT/NP electrodes provide a high short-circuit current density (J sc ) and fill factor (FF) while maintaining a constant open-circuit voltage (V oc ), finally disclosing a higher conversion efficiency (η), attributed to the high loading of dye molecules, light scattering ability, low resistance in the photoanode/electrolyte interface, and longer electron lifetimes. In particular, the optimal η was attained with the TONT/NP (18μm) electrode having a V oc of 0.80V, a J sc of 7.80mA/cm2, a FF of 62.7%, and a η of 3.93%. Incidentally, when using a longer TONT film (28μm), η decreases steadily due to the fast charge recombination process. A more detailed discussion is included below. [Copyright &y& Elsevier]

Nickel ions serve in the correct folding and function of microbial enzymes implicated in metabolic processes. Although nickel ions are indispensable for the survival of cells, the intracellular level of nickel ions needs to be properly maintained as excessive levels of nickel ions are toxic. Nur, a nickel-uptake regulator belonging to the Fur family, is a nickel-responsive transcription factor that controls nickel homeostasis and antioxidative response in Streptomyces coelicolor. Nur was purified and crystallized at 295 K. A 2.4 A native data set and a 3.0 A Ni-MAD data set were collected using synchrotron radiation. The Nur crystals belong to space group P3(1), with unit-cell parameters a = b = 78.17, c = 50.39 A. Assuming the presence of two molecules in the asymmetric unit, the solvent content is estimated to be about 54.7%.