Copper-nuclease efficiency correlates with cytotoxicity for the 4-methoxypyrrolic natural products.
The DNA-targeting activities of the 4-methoxypyrrolic natural products, that include prodigiosin (1), tambjamine E (2), and the blue pigment (3), have been compared using fluorescence spectroscopy to study DNA binding and agarose gel electrophoresis to assess their ability to facilitate oxidative copper-promoted DNA cleavage. Fluorescence emission titration of 3 with calf-thymus DNA (CT-DNA) shows that the natural product occupies a site size (n) of ca. two base pairs and possesses an affinity constant (K) of approximately 6x10(5) x M(-1). Similar to prodigiosin (1), the blue pigment 3 was found to facilitate oxidative double-strand DNA (dsDNA) cleavage without the aid of an external reducing agent. Quantitation of ds- (n2) and ss- (n1) breaks provided n1:n2 ratios of approximately 8-12, which were significantly greater than the number expected from the accumulation of ss-breaks (approximately 120). This was contrasted by the nicking activity of tambjamine E (2), which only generates ss-breaks in the presence of copper. The superior copper-nuclease activity of 1 and 3 also correlated with their superior anticancer properties against leukemia (HL-60) cells. These results are discussed with respect to the mode of cytotoxicity by the 4-methoxypyrrolic natural products.
Melvin
M S
MS
Department of Chemistry, Wake Forest University, Winston-Salem, NC 27109-7486, USA.
Wooton
K E
KE
Rich
C C
CC
Saluta
G R
GR
Kucera
G L
GL
Lindquist
N
N
Manderville
R A
RA
D017209:Apoptosis; D001688:Biological Products / Q000737:chemistry / Q000633:toxicity*; D003300:Copper / Q000378:metabolism*; D004247:DNA / Q000737:chemistry / Q000378:metabolism; D004249:DNA Damage; D003851:Deoxyribonucleases / Q000378:metabolism*; D018922:HL-60 Cells; D006801:Humans; D015394:Molecular Structure; D011353:Prodigiosin / Q000633:toxicity; D011758:Pyrroles / Q000737:chemistry / Q000633:toxicity*; D013050:Spectrometry, Fluorescence
D001688:Biological Products; D011758:Pyrroles; D003300:Copper; D004247:DNA; D003851:Deoxyribonucleases; D011353:Prodigiosin