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PubMed1998

Molecular cloning of the actinomycin synthetase gene cluster from Streptomyces chrysomallus and functional heterologous expression of the gene encoding actinomycin synthetase II.

The actinomycin synthetases ACMS I, II, and III catalyze the assembly of the acyl peptide lactone precursor of actinomycin by a nonribosomal mechanism. We have cloned the genes of ACMS I (acmA) and ACMS II (acmB) by hybridization screening of a cosmid library of Streptomyces chrysomallus DNA with synthetic oligonucleotides derived from peptide sequences of the two enzymes. Their genes were found to be closely linked and are arranged in opposite orientations. Hybridization mapping and partial sequence analyses indicate that the gene of an additional peptide synthetase, most likely the gene of ACMS III (acmC), is located immediately downstream of acmB in the same orientation. The protein sequence of ACMS II, deduced from acmB, shows that the enzyme contains two amino acid activation domains, which are characteristic of peptide synthetases, and an additional epimerization domain. Heterologous expression of acmB from the mel promoter of plasmid PIJ702 in Streptomyces lividans yielded a functional 280-kDa peptide synthetase which activates threonine and valine as enzyme-bound thioesters. It also catalyzes the dipeptide formation of threonyl-L-valine, which is epimerized to threonyl-D-valine. Both of these dipeptides are enzyme bound as thioesters. This catalytic activity is identical to the in vitro activity of ACMS II from S. chrysomallus.

Bacterial Proteins↗
PubMedDate not supplied

[Non stacking binding of 7-amino-actinomycin D and actinomycin D to DNA and model nucleotide systems in solutions].

Mechanism of actinomycin D (AMD) and 7-aminoactinomycin D (7AAMD) interaction with DNA and model nucleotide compounds was studied by absorption and fluorescence spectroscopy (steady-state, phase-modulation, and polarization). It was shown that complex formation does not result in energy transfer from photoexcited nucleotides to phenoxazone chromophore of 7AAMD that indicates the absence of stacking-like intercalation. This fact is fundamentally important to explain the biological effect of actinomycin on cells. It was revealed a fundamental difference in the complex-forming properties of AMD and 7AAMD. Thus AMD is capable of binding to guanine micelles to destroy them. 7AAMD forms complexes neither guanine micelles nor polyguanilic acid. 7AAMD binding sites on DNA can differ substantially from AMD binding sites. However, a strong competition is observed between AMD and 7AAMD for binding site in oligonucleotide HP1 used as DNA hairpin model. The efficient diameters of 7AAMD-HP1 complex and free 7AAMD were determined using the Levshin-Perren equation.

Binding Sites↗
PubMed2000

Crystallization and preliminary X-ray diffraction studies of d(ACGTAGCTACGT)2:[actinomycin D, (echinomycin)2] and d(ACGTAGCTACGT)2:[actinomycin D, (triostin A)2] complexes.

A DNA-multiple drug complex, d(ACGTAGCTACGT)(2):[actinomycin D, (echinomycin)(2)] has been crystallized. The crystals belong to the monoclinic space group C2, with unit-cell parameters a = 85.6, b = 72.8, c = 56.6 A, beta = 101.5 degrees at 93 K and Z = 8. The crystal diffracted to 3.0 A resolution along the DNA fiber axis and to 3.5 A resolution in other directions. The Patterson maps indicate that all complexes in the crystal are oriented along their helical axes in the [101;] direction.

Crystallization↗
PubMed1991

[Fusion of protoplasts of inactive variants of 2 producers of actinomycin C and the biosynthesis of an antibiotic of non- actinomycin nature].

Fusion of protoplasts of double auxotrophic mutants of spontaneous inactive variants of two cultures producing actinomycin C, i.e. Streptomyces chrysomalus 305 and Streptomyces sp. 26-115 induced by PEG-600 yielded a number of stable recombinants. One of the recombinants requiring proline for its growth was designated as recPro. Unlike its parent strains, it synthesized an antibiotic substance active against gram-positive bacteria and Saccharomyces cerevisiae. The nature of the substance is under investigation.

Anti-Bacterial Agents↗