ISSN:
0952-3499
Keywords:
Chemistry
;
Biochemistry and Biotechnology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Medicine
Notes:
MPE-Fe(EDTA) footprinting of a novel monocationic bis-furan lexitropsin 6 on a HindIII/EcoRI restriction fragment of pBR322 DNA revealed a series of four-base binding sites (all 5′ → 3′) of (primary) TGTA, TGAA, AAAT, ACAA, TTAT, and (secondary) CTAA, TCGT, TGTA, GTCA, and GGTT. Thus 6 can accept a GC pair at positions 1, 2 or 3 of the binding site with a strict 3′ (4 position) AT requirement. Marked enhancement of cleavage, particularly at GC rich sequences, is observed at regions flanking or even up to 18 base pairs remote from a given binding site. The non-exchangeable and imino 1H NMR resonances of the 1:1 complex and d-[CATGGCCATG]2 were assigned using a combination of NOE differences, NOESY and COSY techniques. 1H NMR studies (ligand induced chemical shifts and NOE differences) of Lexitropsin 6 with d-[CATGGCCATG]2 show unambiguously the location and orientation of the N to C termini of 6 on the sequence 5′-G5C6C7A8-3′, with the C terminus oriented to A8. This orientation of 6 in the minor groove of 5′-GCCA is confirmed by an NOE observed between H1 2a of 6 and AH8(8). This preference for binding of 6 to the sequence 5′-GCCA when challenged with d-[CATGGCCATG]2 is in accord with the conclusions of the footprinting experiments wherein GC base pairs can be accepted in the first three positions and with a strict 3′ terminus AT reading requirement. Collectively the data support the inference of a GC recognizing capacity for a 2,5-substituted furan moiety within a lexitropsin. The 1H NMR data indicate that the decadeoxyribonucleotide duplex exists in the B conformation in both the 1:1 complex and the free from. The apparent binding constant of 6 to calf thymus DNA is 1.68 × 105 M-1 whereas netropsin under similar conditions gives a value of 1.85 × 107 M-1. This suggests that if advantage is to be taken of the GC recognizing property of a 2,5-substituted furan in longer lexitropsins it should be flanked by more strongly bound moieties.
Additional Material:
9 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jmr.300020206
