From cultures of Yersinia enterocolitica H1852, an iron‐complexing and iron‐transporting compound named yersiniabactin was isolated. The structure of the siderophore was determined by a variety of spectroscopic methods, including 2D NMR experiments on the metal‐free ligand as well as its gallium complex. The metal‐free ligand, derivatives, as well as iron and gallium complexes were examined by high‐resolution FAB‐MS, API‐MS, API‐MS/MS and GC‐MS. The novel siderophore contains a benzene and a thiazolidine ring, as well as two thiazoline rings (Figure 1). Its stereochemistry is noteworthy for the presence of five chiral centers, one of which is considerably epimerized. The compound forms stable complexes with trivalent cations such as ferric iron and gallium.

Novel linear hydroxamate/hydroxycarboxylate siderophores from strains of Pseudomonas cepacia were isolated and named ornibactins. The ornibactins represent modified tetrapeptide siderophores, possessing the sequence L-Orn1(N delta-OH, N delta-acyl)-D-threo-Asp(beta-OH)-L-Ser-L-Orn4(N delta-OH, N delta-formyl)-1,4-diaminobutane. The N delta-acyl groups of Orn1(N delta-OH, N delta-acyl) may vary and represent the three acids 3-hydroxybutanoic acid, 3-hydroxyhexanoic acid and 3-hydroxyoctanoic acid, leading to a mixture of three different ornibactins, designated according to their acyl chain length as ornibactin-C4, ornibactin-C6 and ornibactin-C8. Each of the siderophores is accompanied by a small amount of a more hydrophilic component with a 16 a.m.u. higher mass. The structure elucidation was based on results from gas chromatography amino acid analysis, electrospray mass spectrometry, and one- and two-dimensional nuclear magnetic resonance techniques.

The human single-stranded DNA-binding protein, replication protein A (RPA), is regulated by the N-terminal phosphorylation of its 32-kDa subunit, RPA2. RPA2 is hyperphosphorylated in response to various DNA-damaging agents and also phosphorylated in a cell-cycle-dependent manner during S- and M-phase, primarily at two CDK consensus sites, S23 and S29. Here we generated two monoclonal phospho-specific antibodies directed against these CDK sites. These phospho-specific RPA2-(P)-S23 and RPA2-(P)-S29 antibodies recognized mitotically phosphorylated RPA2 with high specificity. In addition, the RPA2-(P)-S23 antibody recognized the S-phase-specific phosphorylation of RPA2, suggesting that during S-phase only S23 is phosphorylated, whereas during M-phase both CDK sites, S23 and S29, are phosphorylated. Immunofluorescence microscopy revealed that the mitotic phosphorylation of RPA2 starts at the onset of mitosis, and dephosphorylation occurs during late cytokinesis. In mitotic cells treated with ionizing radiation (IR), we observed a rapid hyperphosphorylation of RPA2 in addition to its mitotic phosphorylation at S23 and S29, associated with a significant change in the subcellular localization of RPA. Our data also indicate that the RPA2 hyperphosphorylation in response to IR is facilitated by the activity of both ATM and DNA-PK, and is associated with activation of the Chk2 pathway.

The screening for growth inhibitors against Bacillus subtilis revealed a peptide antibiotic produced by Streptomyces griseoflavus TÜ 4072. Very high yields of the antibiotic named aborycin were obtained by cultivation in a medium containing soybean meal and sucrose. Isolation from the mycelium was carried out by a combination of extraction and gel chromatography. Preparative HPLC yielded the uniform antibiotic. The structure elucidation was based on GC amino acid analysis on a chiral phase, automated Edman degradation, electrospray tandem mass spectrometry and two‐dimensional NMR (TOCSY, ROESY, HSQC, HMBC). Aborycin represents a 21‐peptide that is cyclized from the side chain of Asp9 to the N‐terminus of Cys1. Two disulfide bonds Cys1 to Cys13 and Cys7 to Cys19 form a tricyclic structure consisting exclusively of protein amino acids. The peptide antibiotic aborycin was found to be identical with a HIV protease inhibitor isolated recently from Streptomyces SP 9440.

The screening for growth inhibitors against Bacillus subtilis revealed a peptide antibiotic produced by Streptomyces griseoflavus TU 4072. Very high yields of the antibiotic named aborycin were obtained by cultivation in a medium containing soybean meal and sucrose. Isolation from the mycelium was carried out by a combination of extraction and gel chromatography. Preparative HPLC yielded the uniform antibiotic. The structure elucidation was based on GC amino acid analysis on a chiral phase, automated Edman degradation,The Streptomyces griseoflavus strain TU 4072 was isolated from a soil sample collected in Alice Springs, Australia. Due to this origin of the producing strain the isolated antibiotic was named aborycin. Cultivation using soybean meal as nitrogen source and sucrose as carbon source gave high yields of aborycin. For the isolation of the antibiotic the aqueous methanolic extract of the mycelium was first extracted with ethyl acetate and then with l-butanol. Gel chromatography of the 1-butanol extract followed by preparative HPLC gave 271 mg of pure aborycin out of 5 liters of culture broth. After treatment with Ehrlich's reagent the antibiotic gave a blue spot on TLC plates (Rf = 0.47, 1-butanoYethanoVwater, 6:2:2). The Rf value was similar to the one of tryptophan. Aborycin inhibited the growth of Bacillus subtilis ATCC 6633 at a minimum inhibition concentration (MIC) of 20 pg/ml, Bacillus brevis ATCC 9999 (MIC 25 pglml), Staphylococcus aureus ETH 2070 (MIC 15 pglml), Pseudomonas saccharophila ATCC 15946 (MIC 15 pg/ml), and of Streptomyces viridochromogenes TU 57 (MIC 2 pglml) but was inactive against Escherichia coli K12, Salmonella typhimurium TU 5108, Mucor hiemalis TU 179/180, Mucor miehi TU 284, and Yarrowia lipolytica TU 5054.