NMR studies of echinomycin bisintercalation complexes with d(A1-C2-G3-T4) and d(T1-C2-G3-A4) duplexes in aqueous solution: sequence-dependent formation of Hoogsteen A1 x T4 and Watson-Crick T1 x A4 base pairs flanking the bisintercalation site

Journal Article · Tue Mar 08 00:00:00 EST 1988 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00405a054· OSTI ID:5381102

Gao, X; Patel, D J

The authors report on two-dimensional proton NMR studies of echinomycin complexes with the self-complementary d(A1-C2-G3-Tr) and d(T1-C2-G3-A4) duplexes in aqueous solution. The exchangeable and nonexchangeable antibiotic and nucleic acid protons in the 1 echinomycin per tetranucleotide duplex complexes have been assigned from analyses of scalar coupling and distance connectivities in two-dimensional data sets records in H/sub 2/O and D/sub 2/O solution. An analysis of the intermolecular NOE patterns for both complexes combined with large upfield imino proton and large downfield phosphorus complexation chemical shift changes demonstrates that the two quinoxaline chromophores of echinomycin bisintercalate into the minor groove surrounding the dC-dG step of each tetranucleotide duplex. Further, the quinoxaline rings selectively stack between A1 and C2 bases in the d(ACGT) complex and between T1 and C2 bases in the d(TCGA) complex. The intermolecular NOE patterns and the base and sugar proton chemical shifts for residues C2 and G3 are virtually identical for the d(ACGT) and d(TCGA) complexes. A large set of intermolecular contacts established from nuclear Overhauser effects (NOEs) between antibiotic and nucleic acid protons in the echinomycin-tetranucleotide complexes in solution are consistent with corresponding contacts reported for echinomycin-oligonucleotide complexes in the crystalline state. The authors demonstrate that the G x G base pairs adopt Watson-Crick pairing in both d(ACGT) and d(TCGA) complexes in solution. By contrast, the A1 x T4 base pairs adopt Hoogsteen pairing for the echinomycin-d(A1-C2-G3-Tr) complex while the T1 x A4 base pairs adopt Watson-Crick pairing for the echinomycin-d(T1-C2-G3-A4) complex in aqueous solution. These results emphasize the role of sequence in discriminating between Watson-Crick and Hoogsteen pairs at base pairs flanking the echinomycin bisintercalation site in solution.

• Research Organization: Columbia Univ., New York, NY (USA)
• OSTI ID: 5381102
• Journal Information: Biochemistry; (United States), Vol. 27:5
• Country of Publication: United States
• Language: English

Related Subjects

62 RADIOLOGY AND NUCLEAR MEDICINE
ANTIBIOTICS
NUCLEAR MAGNETIC RESONANCE
OLIGONUCLEOTIDES
AQUEOUS SOLUTIONS
CHEMICAL SHIFT
CLATHRATES
COMPLEXES
HEAVY WATER
PROTONS
WATER
ANTI-INFECTIVE AGENTS
BARYONS
DISPERSIONS
DRUGS
ELEMENTARY PARTICLES
FERMIONS
HADRONS
HYDROGEN COMPOUNDS
MAGNETIC RESONANCE
MIXTURES
NUCLEIC ACIDS
NUCLEONS
ORGANIC COMPOUNDS
OXYGEN COMPOUNDS
RESONANCE
SOLUTIONS
550601* - Medicine- Unsealed Radionuclides in Diagnostics