1BCB

INTRAMOLECULAR TRIPLEX, NMR, 10 STRUCTURES

Summary for 1BCB

• Entry DOI: 10.2210/pdb1bcb/pdb
• Related: 1BCE 1BWG
• Descriptor: DNA (5'-D(*AP*GP*AP*AP*GP*A)-3'), DNA (5'-D(*TP*CP*TP*TP*CP*T)-3') (2 entities in total)
• Functional Keywords: deoxyribonucleic acid, dna triplex, dna
• Total number of polymer chains: 3
• Total formula weight: 5366.64

Authors

Asensio, J.L.,Brown, T.,Lane, A.N. (deposition date: 1998-04-29, release date: 1998-08-12, Last modification date: 2024-05-22)

Primary citation

Asensio, J.L.,Brown, T.,Lane, A.N.
Comparison of the solution structures of intramolecular DNA triple helices containing adjacent and non-adjacent CG.C+ triplets.
Nucleic Acids Res., 26:3677-3686, 1998

PubMed Abstract: The solution conformations of the intramolecular triple helices d(AGAAGA-X-TCTTCT-X-TC+TTC+T) and d(AAGGAA-X-TTCCTT-X-TTC+C+TT) (X = non-nucleotide linker) have been determined by NMR.1H NMR spectra in H2O showed that the third strand cytosine residues are fully paired with the guanine residues, each using two Hoogsteen hydrogen bonds. Determination of the13C chemical shifts of the cytosine C6 and C5 and their one-bond coupling constants (1 J CH) conclusively showed that the Hoogsteen cytosine residues are protonated at N3. The global conformations of the two molecules determined with >19 restraints per residue are very similar (RMSD = 0.96 A). However, some differences in local conformation and dynamics were observed for the central two base triplets of the two molecules. The C N3H were less labile in adjacent CG.C+triplets than in non-adjacent ones, indicating that the adjacent charge does not kinetically destabilize these triplets. The sugar conformations of the two adjacent cytosine residues were different and the 5'-residue was atypical of protonated cytosine. Hence, there are subtle effects of the interaction between two adjacent cytosine residues. The central two purines in each sequence showed non-standard backbone conformations, averaging between gamma approximately 60 degrees and gamma approximately 180 degrees. This may be related to the difference in the dependence of the thermodynamic stability on pH observed for these two sequences.

PubMed: 9685482
DOI: 10.1093/nar/26.16.3677

Experimental method

SOLUTION NMR