TwoGram-negative bacteria were found to produce the newantibacterial antibiotics TAN-1 057 A, B, C arid D. The producing bacteria were characterized and designated as Flexibacter sp. PK-74 and PK-176.Theseantibiotics wereactive against Gram-negativeand Gram-positivebacteria, including methicillin-resistant Staphylococcus aureus. TAN-1 057 A inhibited protein biosynthesis in Escherichia coli and S. aureus.It showed excellent protective effects against an experimental methicillin-resistant S. aureus infection in mice.

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Insulin stimulates translocation of glucose transporter isoform type 4 (GLUT4) and the insulin-responsive aminopeptidase (IRAP) from an intracellular storage pool to the plasma membrane in muscle and fat cells. A role for the cytoskeleton in insulin action has been postulated, and the insulin signaling pathway has been well investigated; however, the molecular mechanism by which GLUT4/IRAP-containing vesicles move from an interior location to the cell surface in response to insulin is incompletely understood. Here, we have screened for IRAP-binding proteins using a yeast two-hybrid system and have found that the C-terminal domain of FHOS (formin homolog overexpressed in spleen) interacts with the N-terminal cytoplasmic domain of IRAP. FHOS is a member of the Formin/Diaphanous family of proteins that is expressed most abundantly in skeletal muscle. In addition, there are two novel types of FHOS transcripts generated by alternative mRNA splicing. FHOS78 has a 78-bp insertion and it is expressed mainly in skeletal muscle where it may be the most abundant isoform in humans. The ubiquitously expressed FHOS24 has a 24-bp insertion encoding an in-frame stop codon that results in a truncated polypeptide. It is known that some formin family proteins interact with the actin-binding profilin proteins. Both FHOS and FHOS78 bound to profilin IIa via their formin homology 1 domains, but neither bound profilin I or IIb. Overexpression of FHOS and FHOS78 resulted in enhanced insulin-stimulated glucose uptake in L6 cells to similar levels. However, overexpression of FHOS24, lacking the IRAP-binding domain, did not affect insulin-stimulated glucose uptake. These findings suggest that FHOS mediates an interaction between GLUT4/IRAP-containing vesicles and the cytoskeleton and may participate in exocytosis and/or retention of this membrane compartment.

Twonewnucleotide antibiotics, fosfadecin and fosfocytocin, have been isolated from the culture filtrates of Pseudomonas viridiflava PK-5and Pseudomonasfluorescens PK-52, respectively. These antibiotics werepurified by columnchromatographies using adsorption, gel filtration and ion exchange resins. Onthe basis of the spectroscopic and degradation studies, the chemical structures of fosfadecin and fosfocytocin were determined. These antibiotics were either enzymatically or chemically hydrolyzed to generate fosfomycin and a new antibiotic, fosfoxacin, which are also produced in the culture filtrates. They showed antibacterial activity against Gram-positive and Gram-negative bacteria. The antibacterial activity of these nucleotide antibiotics was weaker than that of fosfomycin and fosfoxacin.In the course of screening for new antibiotics which inhibit bacterial cell wall biosynthesis, we found that new nucleotide antibiotics, fosfadecin (1) and fosfocytocin (2) were produced by Gram-negative bacteria. These two antibiotics were converted to their nucleoside 5'-monophosphates (5 and 6, respectively), in addition, fosfadecin yielded fosfomycin1) (3) and fosfocytocin yielded a new antibiotic, fosfoxacin (4) (Fig.1).The present paper describes the producing organisms, fermentation, isolation, structure determination and biological activity of these nucleotide antibiotics. Producing OrganismThe fosfadecin-producing strain PK-5 was isolated from a bamboo leaf collected in Yumesaki-cho, Shikama-gun, Hyogo Prefecture, Japan. The fosfocytocin-producing strain PK-52 was isolated from a soil sample collected in Shimotsu-cho, Kaiso-gun, Wakayama Prefecture, Japan.The taxonomical characteristics of strains PK-5 and PK-52 are summarized in Table 1.. Strains PK-5 and PK-52 are Gram-negative rods, motile by polar flagella, metabolize glucose oxidatively, and are catalase-positive.The mol % G+Cof the DNAis 65.1 and 63.7, respectively. Strains PK-5 and PK-52 are considered to belong to the genus Pseudomonas.Strain PK-5 does not accumulate poly-/Miydroxybutyrate as a carbon reserve material, and it produces fluorescent pigment. This strain is also negative for arginine dihydrolase and oxidase. These properties indicate that it should be classified as Pseudomonassyringae or Pseudomonasviridiflava. As strain PK-5 has a polar flagellum, it was identified as P. viridiflava and designated P. viridiflava PK-5.Strain PK-52 does not accumulate poly-/?-hydroxybutyrate and produces fluorescent pigment. It has more than one flagella. It is arginine dihydrolase positive and hydrolyzes gelatin. Fromthese characteristics, 1 Fosfadecin was presented as TAN-930 in Jpn.

In the search for new beta-lactam antibiotics of natural origin, the discoveries of cephamycins and sulfazecins (monobactams) were important turning points in that they accelerated many screening efforts aimed at other new compounds. In our target-directed screening for beta-lactam antibiotics using beta-lactam hypersensitive mutants, we have examined Gram-negative bacteria isolated from natural habitats and have recently reported several types of beta-lactam antibiotics such as cephabacins and formadicins. Here we report a novel antibiotic, lactivicin, found using this system. Although lactivicin has various biological activities commonly observed in beta-lactam antibiotics, it does not possess a beta-lactam ring in its molecule, but has the unique structure of a dicyclic dipeptide.