Four new polyketides, named rubiginone D₂ (2), 4-O-acetyl-rubiginone D₂ (3), rubiginone H (6) and rubiginone I (7) were isolated from the cultures of Streptomyces sp. (strain Gö N1/5). Their structures were established by a detailed spectroscopic analysis. The absolute configuration of 3 was determined by derivatization with chiral acids (Helmchen's method). The rubiginones inhibit the growth of some Gram-positive bacteria and are cytostatically active against different tumor cell lines.

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Strain TP-A0248 which produces two new Cdc25B tyrosine phosphatase inhibitors and also possessing antifungal activity, designated nocardiones A (1) and B (2), was considered to belong to the genus Nocardia on the basis of literature comparison of chemotaxonomic properties. The nocardiones were isolated by solvent extraction of fermentation broth of Nocardia sp. TP-A0248 and purified by the conventional column chromatography. Spectroscopic studies led to determination that 1 and 2 belong to a class compound of naphtho[1, 2-b]furan-4, 5-diones. Compound 1 inhibited the activity of Cdc25B, PTP1B and FAP-1 protein tyrosine phosphatases at a concentration of 10μM. It also showed moderate in vitro antifungal and cytotoxic activity.

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A novel, potent and selective inhibitor of bacterial tyrosyl tRNA synthetase, designated SB-219383 has been isolated from Micromonospora sp. NCIMB 40684. The fermentation, isolation and some properties are described, whilst the structure determination is described in the succeeding paper¹⁾. SB-219383 showed competitive, inhibitory activity against a Staphylococcus tyrosyl tRNA synthetase, with an IC₅₀ of <1nM, and exhibited weak in vitro activity against some Streptococcus sp.

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A novel tyrosyl tRNA synthetase inhibitor, SB-219383, has been isolated from a Micromonospora sp. The structure of SB-219383 has been elucidated by a combination of derivatisation, spectroscopic and other analytical techniques and found to be N-(L-tyrosyl)-2-amino[1(S^*), 3(S^*), 4(S^*), 5(R^*), 8(R^*)-2, 4, 5, 8-tetrahydroxy-7-oxa-2-azabicyclo[3.2.1]oct-3-yl]acetic acid (1).

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Two novel inhibitors of isoleucyl tRNA synthetase designated SB-203207 and SB-203208 have been detected in the culture of a new Streptomyces species. The fermentation, isolation and some properties of the inhibitors are described.

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Two novel isoleucyl tRNA synthetase inhibitors, SB-203207 and SB-203208 have been isolated from a Streptomyces sp. and found to be structurally related to altemicidin. Structures of SB-203207 and SB-203208 have been deduced by a combination of spectroscopic techniques, derivatisation, hydrolysis studies and found to be 4-(aminocarbonyl)-7-{[(2-amino-3-methylpentanoyl)aminosulphonyl]acetamido}-2, 4a, 5, 6, 7, 7a-hexahydro-6-hydroxy-2-methyl-1H-2-pyrindine-7-carboxylic acid (1) and 4-(aminocarbonyl)-7-{[(2-amino-3-methyl pentanoyl)-aminosulphonyl]acetamido}-2, 4a, 5, 6, 7, 7a-hexahydro-6-(2-amino-3-phenylbutanoyl oxy)-2-methyl-1H-2-pyrindine-7-carboxylic acid (2), respectively.

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We previously reported that a 7.6-kb DNA fragment from Streptomyces kasugaensis M338-M1, a kasugamycin (KSM) producer, included KSM acetyltransferase gene (kac³³⁸) and some other genes possibly involved in KSM biosynthesis. As an extension of that study, a 10-kb SacI-KpnI DNA fragment, located 5-15-kb upstream of kac³³⁸, was cloned and a 4.2-kb SacI-EcoRI fragment therefrom was sequenced, revealing one incomplete (designated ORF J) and three complete open reading frames (designated kasK, kasL and kasM). The coding frames of kasK, L and M overlap one another with terminator/initiator ATGA sequence. RT-PCR analysis of a DNA region including kasKLM indicated the presence of one transcript that is long enough to span the three genes. The kasK gene potentially encodes an ATP-binding protein of the ATP-binding cassette (ABC) transporter superfamily. Homology search for the deduced KasK protein shows similarity to other ABC transporters involved in self-resistance of a mithramycin and possibly doxorubicin producer strain. The kasL and kasM genes encode different integral membrane proteins, both having six putative transmembrane helices. An expression plasmid for kasKLM (pTV-KLM) was constructed and these genes were expressed in E. coli JM109, which had been sensitive to KSM. The transformant acquired resistance to KSM, suggesting that KasK, L and M proteins as a set in S. kasugaensis M338-M1 pump out KSM to protect the producer from its toxic metabolite.

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The nikO gene encoding a putative enolpyruvyl transferase has been identified within the Streptomyces tendae Tü901/8c nikkomycin gene cluster. nikO encodes a deduced protein of 471 amino acid residues which exhibits significant sequence similarity to UDP-N-acetylglucosamine enolpyruvyl transferase and 5-enol-pyruvylshikimate 3-phosphate synthase from various origin. The nikO gene was inactivated by inserting a kanamycin resistance cassette; the mutant did not produce biologically active nikkomycins I, J, X, and Z nor the nucleoside moieties, nikkomycins C_x and C_z, but accumulated the novel component RT 2.0. RT 2.0 has been isolated from culture filtrate and its structure was determined by using mass spectrometry and NMR analyses as ribofuranosyl-4-formyl-4-imidazolone which represents a novel nucleoside. The putative activity of the nikO gene product in nikkomycin biosynthesis will be discussed.

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In the course of our bioconversion studies on the derivatives of an indolocarbazole, J-104303, Saccharothrix aerocolonigenes ATCC39243 was found to convert J-104303, which was added into the culture medium, to its glycosylated derivative, J-1093 84. In order to clone the gene having the ability to convert J-104303 to J-109384, a library of Saccharothrix aerocolonigenes ATCC39243 DNA fragments was constructed using Streptomyces lividans TK21 and pIJ702 as host strain and vector, respectively. By examining more than 5, 000 transformants, one was found to convert J-104303 to J-109384. Sequence analysis of the inserted DNA fragment revealed an open reading frame with 1, 245 base pairs, named ngt. The transformant containing this ngt gene was also found to introduce a D-glucose moiety into 6-N-methylarcyriaflavin C. Furthermore, when ngt was introduced into Streptomyces mobaraensis BA13793, a producer of J-104303, the resulting transformant produced J-109384 directly.

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Synthesis of new tricyclic carbapenems (trinems) with a pyrrolidinyl moiety at the C-4 position of the tricyclic ring and their antimicrobial activities were studied. These trinems showed potent activities against Gram-positive bacteria including methicillin-resistant Staphylococcus aureus (MRSA). Among them, (4R)-[(S)-pyrrolidin-3-ylthiomethyl]trinem (14a) exhibited good activity against MRSA in vitro and in vivo.

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