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Gaegurin 5 (GGN5) is a cationic 24-residue anti-microbial peptide isolated from the skin of a Korean frog, Rana rugosa. It contains a central proline residue and an intra-residue disulphide bridge in its C-terminus, which are common to the anti-microbial peptides found in Ranidae. We determined the solution structure of GGN5 bound to SDS micelles for the first time and investigated the role of proline, cysteine and a disulphide bridge on the structure and activity of GGN5. GGN5 adopts an amphipathic alpha-helical structure spanning residues 3-20 kinked around Pro-14, which allows the hydrophobic residues to reside in the concave helical region, and a disulphide-bridged loop-like conformation in its C-terminus. By replacement of proline with alanine (PAGGN5), a straight and rigid helix was formed in the central region and was more stable than the kinked helix. Reduction of a disulphide bridge in the C-terminus (GGN5SH) maintained the loosely ordered loop-like conformation, while the replacement of two cysteines with serines (CSGGN5) caused the C-terminal conformation to be completely disordered. The magnitude of anti-microbial activity of the peptides was closely related to their helical stability in the order PAGGN5>GGN5>GGN5SH>CSGGN5, suggesting that the helical stability of the peptides is important for anti-microbial activity. On the other hand, the significant increase of haemolytic activity of PAGGN5 implies that a helical kink of GGN5 could be involved in the selectivity of target cells. The location of GGN5 and PAGGN5, analysed using paramagnetic probes, was mainly at the surface of SDS micelles, although the location of the N-terminal region was slightly different between them.

The in vitro and in vivo activities of DW286, a novel fluoronaphthyridone with potent antibacterial activity, were compared with those of ciprofloxacin, gemifloxacin, sparfloxacin, and trovafloxacin. Against gram-positive bacteria, such as Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pneumoniae, and Enterococcus faecalis, the in vitro activity of DW286 was stronger than that of any other reference antibiotic. Against gram-negative bacteria, the activity of DW286 was similar to those of trovafloxacin and gemifloxacin but was weaker than that of ciprofloxacin. In a mouse systemic infection caused by three S. aureus strains, including methicillin-resistant S. aureus and quinolone-resistant S. aureus (QRSA), DW286 demonstrated the most potent activity, as found in vitro. Specially, DW286 is >8-fold more active against QRSA than the other fluoroquinolones. And the 50% protective doses for DW286 were correspondent with the in vitro activities.The quinolones have evolved from agents used solely for the treatment of urinary tract infections to molecules with potent activity against a wide spectrum of significant bacterial pathogens. Progressive modifications in their molecular configurations have improved both the spectrum and potency of their in vitro activities (2). These compounds have been successfully used in clinics for a decade. The targets in fluoroquinolone research during the last few years include improving the pharmacokinetic properties, increasing the activity against grampositive cocci and anaerobes and against fluoroquinolone-resistant strains, and improving activity against nonfermentative gram-negative species (1,4,5,6). In addition, the increasing pathogen resistance to antimicrobial agents is a cause of concern. This increase in the resistance to fluoroquinolone emphasizes the importance of the continued development of new structural candidates (3,4,5,6,7). The use of newer fluoroquinolone derivatives will potentially contribute to decreasing the spread of resistance to other antimicrobial agents by reducing the selective pressure on other antibiotic groups (5). New candidates have been developed in an attempt to help improve this situation. DW286, 7-[3-(aminomethyl)-4-(methoxyimino)-3-methyltetrahydro-1H-1-pyrrolyl]-1-cyclopropyl-6-fluoro-4-oxo-1, 4-dihydro [1,8]naphthyridine-3-carboxylic acid hydrochloric acid salt, is a novel fluoronaphthyridone antibacterial agent that was synthesized for this purpose (Fig. 1). In this study, we determined the in vitro activity of DW286 in several groups of clinical isolates and compared it with those of ciprofloxacin, gemifloxacin, sparfloxacin, and trovafloxacin. We also compared the in vivo protective efficacy of DW286 with those of the fluoroquinolones against a systemic infection in mice.The studied compounds were obtained as follows: DW286, ciprofloxacin, sparfloxacin, and gemifloxacin were synthesized at the R & D Center, Dong Wha Pharmaceutical Company, Anyang City, Korea. Trovafloxacin was provided by Pfizer Pharmaceuticals, New York,...

Arylsulfate sulfotransferase (ASST) transfers a sulfate group from a phenolic sulfate ester to a phenolic acceptor substrate. In the present study, the gene encoding ASST was cloned from a genomic library copy of Citrobacter freundii, subcloned into the vector pGEM3Zf(-) and sequenced. Sequencing revealed two contiguous open reading frames (ORF1 and ORF2) on the same strand and based on amino acid sequence homology, they were designated as astA and dsbA, respectively. The amino acid sequence of astA deduced from C. freundii was highly similar to that of the Salmonella typhimurium, Enterobacter amnigenus, Klebsiella, Pseudomonas putida, and Campylobacter jejuni, encoded by the astA genes. However, the ASST activity assay revealed different acceptor specificities. Using p-nitrophenyl sulfate (PNS) as a donor substrate, alpha-naphthol was found to be the best acceptor substrate, followed by phenol, resorcinol, p-acetaminophen, tyramine and tyrosine.

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