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α-Helix E of Spo0A Is Required for δA- but Not for dH-Dependent Promoter Activation in Bacillus subtilis. Amrita Kumar, 2004.At the onset of endospore formation in Bacillus subtilis, the DNA binding protein Spo0A activates transcription from two typesof promoters . The first type includes the spoIIG and spoIIE promoters, which are used by δA-RNA polymerase, whereas the secondtype includes the spoIIA promoter, which is used by RNA polymerasecontaining the secondary sigma factor δH . Previous genetic analyseshave identified specific amino acids in α-helix E of Spo0A thatare important for activation of Spo0A-dependent, δA-dependent promoters . However, these amino acids are not required for activation of the δH-dependent spoIIA promoter . We now report the effectsof additional single-amino-acid substitutions and the effectsof deletions in α-helix E . The effects of alanine substitutionsrevealed one new position [239] in Spo0A that appears to bespecifically required for activation of the δA-dependent promoters.Based on the effects of a deletion mutation, we suggest that α-helix E in Spo0A is not directly involved in interaction with δH-RNA polymerase. A 7-Deaza-Adenosine Analog Is a Potent and Selective Inhibitor of Hepatitis C Virus Replication with Excellent Pharmacokinetic Properties. David B. Olsen, 2004.Improved treatments for chronic hepatitis C virus (HCV) infection are needed due to the suboptimal response rates and deleterious side effects associated with current treatment options . The triphosphates of 2'-C-methyl-adenosine and 2'-C-methyl-guanosine were previously shown to be potent inhibitors of the HCV RNA-dependent RNA polymerase (RdRp) that is responsible for the replication of viral RNA in cells . Here we demonstrate that the inclusion of a 7-deaza modification in a series of purine nucleoside triphosphates results in an increase in inhibitory potency against the HCV RdRp and improved pharmacokinetic properties . Notably, incorporation of the 7-deaza modification into 2'-C-methyl-adenosine results in an inhibitor with a 20-fold-increased potency as the 5'-triphosphate in HCV RdRp assays while maintaining the inhibitory potency of the nucleoside in the bicistronic HCV replicon and with reduced cellular toxicity . In contrast, while 7-deaza-2'-C-methyl-GTP also displays enhanced inhibitory potency in enzyme assays, due to poor cellular penetration and/or metabolism, the nucleoside does not inhibit replication of a bicistronic HCV replicon in cell culture . 7-Deaza-2'-C-methyl-adenosine displays promising in vivo pharmacokinetics in three animal species, as well as an acute oral lethal dose in excess of 2,000 mg/kg of body weight in mice . Taken together, these data demonstrate that 7-deaza-2'-C-methyl-adenosine is an attractive candidate for further investigation as a potential treatment for HCV infection . In Vitro Activity of the New Quinolone WCK 771 against Staphylococci. Michael R. Jacobs, 2004.The activity of WCK 771, an experimental quinolone developed to overcome quinolone resistance in staphylococci and other bacteria, was determined against quinolone-susceptible and -resistant Staphylococcus aureus and S . epidermidis . WCK 771 MICs for 50 and 90% of the strains tested (MIC50 and MIC90, respectively) were 0.008 and 0.015 µg/ml for S . aureus (n = 43) and 0.015 and 0.03 µg/ml for S . epidermidis (n = 44) for quinolone-susceptible isolates, compared to ciprofloxacin values of 0.12 and 0.25 µg/ml and 0.25 and 0.5 µg/ml, respectively . Values for levofloxacin were 0.12 and 0.25 µg/ml and 0.12 and 0.25 µg/ml, those for clinafloxacin were 0.015 and 0.03 µg/ml and 0.015 and 0.03 µg/ml, those for moxifloxacin were 0.03 and 0.06 µg/ml and 0.06 and 0.12 µg/ml, and those for gatifloxacin were 0.06 and 0.12 µg/ml and 0.12 and 0.25 µg/ml, respectively . The WCK 771 MIC50 and MIC90, respectively, were 0.5 and 1 µg/ml for both species of staphylococci (n = 73 for S . aureus, n = 70 for S . epidermidis) for isolates highly resistant to ciprofloxacin (MIC50 and MIC90, >32 and >32 µg/ml, respectively) . Values for levofloxacin were 8 and 32 µg/ml and 8 and 32 µg/ml, those for clinafloxacin were 1 and 2 µg/ml and 0.5 and 2 µg/ml, those for moxifloxacin 4 and >4 µg/ml and 4 and >4 µg/ml, and those for gatifloxacin were 4 and >4 µg/ml and 2 and >4 µg/ml, respectively . WCK 771 and clinafloxacin demonstrated MICs of 1 µg/ml against three vancomycin-intermediate strains . WCK 771 showed concentration-independent killing for up to 24 h at 2, 4, and 8 times the MICs against quinolone-resistant staphylococci and was also bactericidal after 8 h for high-density inocula (108 CFU/ml) of quinolone-resistant strains at 5 µg/ml, whereas moxifloxacin at 7.5 µg/ml was bacteriostatic . WCK 771 was not a substrate of the NorA efflux pump as evident from the similar MICs against both an efflux-positive and an efflux-negative strain . Overall, WCK 771 was the most potent quinolone tested against the staphylococci tested, regardless of quinolone susceptibility .
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