Comparative studies of coordination properties of puromycin and puromycin aminonucleoside towards copper(II) ions

Protonation equilibria of puromycin (PM) and puromycin aminonucleoside (PAN) and their coordination by copper(II) ion were studied in solution by potentiometry, electronic absorption spectroscopy (UV-Vis), circular dichroism (CD), electron paramagnetic resonance (EPR) and mass spectrometry. For puromycin four mononuclear complexes were found, with stoichiometries Cu(PM)2+, CuH(-1)(PM)+, CuH(-2)(PM) and CuH(-3)(PM)(-). In each of them the Cu(II) ion was bound in the peptidic-like manner, the differences of stoichiometries are a consequence of subsequent deprotonations of the sugar C2'-OH group and the coordinated water molecule. The coordination mode for puromycin aminonucleoside was aminosugar-like. Two dimeric complexes, Cu2H(-1)(PAN)2(2+) and Cu2H(-2)(PAN)2+, and one monomeric CuH(-2)(PAN)2 were found. The N6,N6-dimethyladenine moiety of PAN was not involved in the coordination process due to steric hindrance.

Thepur6gene of the puromycin biosynthetic gene cluster fromStreptomyces albonigerencodes a tyrosinyl-aminonucleoside synthetase

The pur6 gene of the puromycin biosynthetic gene (pur) cluster from Streptomyces alboniger is shown to be essential for puromycin biosynthesis. Cell lysates from this mycelial bacterium were active in linking L-tyrosine to both 3'-amino-3'-deoxyadenosine and N6,N6-dimethyl-3'-amino-3'-deoxyadenosine with a peptide-like bond. Identical reactions were performed by cell lysates from Streptomyces lividans or Escherichia coli transformants that expressed pur6 from a variety of plasmid constructs. Physicochemical and biochemical analyses suggested that their products were tridemethyl puromycin and O-demethylpuromycin, respectively. Therefore, it appears that Pur6 is the tyrosinyl-aminonucleoside synthetase of the puromycin biosynthetic pathway.

Cystocin, a novel antibiotic, produced by Streptomyces sp. GCA0001: biological activities

Cystocin belongs to the class of nucleoside antibiotics from Streptomyces sp. GCA0001. Cystocin showed good activity against gram-positive bacteria, but showed less activity against the gram-negative bacteria. Cystocin exhibited about two to four folds higher activity than puromycin. Especially, cystocin shows relatively strong activity against Streptococcus strains. Cystocin shows quite potent antitumor activity against all of the cells tested showing IC50 values of 0.10 to 0.14 microg/mL. This in vitro result indicates that the cytotoxocity of cystocin is two ten folds more active than puromycin's.

Identification of a set of genes involved in the biosynthesis of the aminonucleoside moiety of antibiotic A201A from Streptomyces capreolus

A novel cosmid (pABC6.5) whose DNA insert from Streptomyces capreolus, the A201A antibiotic producer, overlaps the inserts of the previously reported pCAR11 and pCAR13 cosmids, has been isolated. These two latter cosmids were known to contain the aminonucleoside antibiotic A201A resistance determinants ard2 and ard1, respectively. Together, these three cosmids have permitted the identification of a DNA stretch of 19 kb between ard1 and ard2, which should comprise a large region of a putative A201A biosynthetic (ata) gene cluster. The sequence of the 7 kb upstream of ard1 towards ard2 reveals seven consecutive open reading frames: ataP3, ataP5, ataP4, ataP10, ataP7, ata12 and ataPKS1. Except for the last two, their deduced products present high similarities to an identical number of counterparts from the pur cluster of Streptomyces alboniger that were either known or proposed to be implicated in the biosynthesis of the N6,N6-dimethyl-3'-amino-3'-deoxyadenosine moiety of puromycin. Because A201A contains this chemical moiety, these ataP genes are most likely implicated in its biosynthesis. Accordingly, the ataP4, ataP5 and ataP10 genes complemented specific puromycin nonproducing Deltapur4, Deltapur5 and Deltapur10 mutants of S. alboniger, respectively. Amino acid sequence comparisons suggest that ata12 and ataPKS1 could be implicated in the biosynthesis of the d-rhamnose and alpha-p-coumaric acid moieties of A201A. Further sequencing of 2 kb of DNA downstream of ard1 has disclosed a region which might contain one end of the ata cluster.

Substituted purines elicit differential cytokinetic, molecular and phenotypic effects in HL-60 cells

This study investigated and compared the cytokinetic, phenotypic and molecular effects elicited in HL-60 human leukemic cells by low doses (0.6 microM) of 3 closely related, substituted purines, puromycin (PM), puromycin aminonucleoside (PAN) and 6-dimethylaminopurine (6-DMAP). PM, but not 6-DMAP or PAN, inhibited [14C]leucine incorporation, induced a time-related cytotoxic effect, a G2-arrest, a metaphase-mitotic-arrest, apoptosis and c-myc mRNA superinduction. PAN and 6-DMAP exerted no detectable morphological or cytokinetic effects, although exposure to these drugs resulted in downregulation of c-myc mRNA levels. We suggest that the specific effects exerted by PM relate to the generation of nascent peptidyl-PM complexes by PM, but not by 6-DMAP or PAN.