Evidence for the binding mode of porphyrins to G-quadruplex DNA.
Interactions of porphyrin derivatives 5,10,15,20-tetrakis(N-methylpyridinium-4-yl)-21H,23H-porphyrin (TMPyP4) and 5,10,15,20-tetrakis(N-propylpyridinium-4-yl)-21H,23H-porphyrin (TPrPyP4) with human telomeric AG(3)(T(2)AG(3))(3) G-quadruplex DNAs in 150 mM K(+)-containing buffer in the presence or absence of 40% molecular crowding agent poly(ethylene glycol) (PEG 200) were studied by absorption titration fitting and time-resolved fluorescence spectroscopy. The results show that two TMPyP4 (or TPrPyP4) molecules bind to antiparallel/parallel hybrid structure of AG(3)(T(2)AG(3))(3) G-quadruplex by end-stacking and outside groove binding modes in the absence of PEG. Interestingly, in the presence of PEG one porphyrin molecule is stacked between two parallel AG(3)(T(2)AG(3))(3) G- quadruplexes to form a sandwich structure, another porphyrin molecule is bound to the groove of the G-quadruplex. The interactions of TMPyP4 with different structures of AG(3)(T(2)AG(3))(3) G-quadruplex are non cooperative, the binding constants of two independent binding sites are 1.07 x 10(6) and 4.42 x 10(8) M(-1) for an antiparallel/parallel hybrid structure of AG(3)(T(2)AG(3))(3), 8.67 x 10(5) and 2.26 x 10(8) M(-1) for parallel-stranded AG(3)(T(2)AG(3))(3) G-quadruplex. Conversely, the two binding sites are cooperative for TPrPyP4, the apparent association constants are 5.58 x 10(6) and 1.24 x 10(7) M(-1) for parallel-stranded and antiparallel/parallel hybrid structures of AG(3)(T(2)AG(3))(3) G-quadruplex, respectively.
Wei
Chunying
C
Institute of Molecular Science, Shanxi University, Taiyuan, 030006, China. weichuny@sxu.edu.cn
Jia
Guoqing
G
Zhou
Jun
J
Han
Gaoyi
G
Li
Can
C
D000042:Absorption; D002021:Buffers; D002942:Circular Dichroism; D004247:DNA / Q000737:chemistry*; D054856:G-Quadruplexes; D006801:Humans; D008543:Melanins; D011092:Polyethylene Glycols / Q000737:chemistry; D011166:Porphyrins / Q000737:chemistry*; D013050:Spectrometry, Fluorescence
D002021:Buffers; D008543:Melanins; D011166:Porphyrins; C030524:fluorescent age pigment; D011092:Polyethylene Glycols; D004247:DNA