Interaction of tryptophan containing oligopeptide with d-CpGpCpG by proton NMR.
The binding of tetrapeptide Lys-Trp-Gly-Lys OtBu to d-CpGpCpG has been studied by proton NMR at 90 MHz and 400 MHz. Changes in chemical shift have been observed in the temperature range 275-335 K. Interaction with tetrapeptide Lys-Ala-Ala-Lys NHEt has been studied in order to ascertain the contribution to changes in chemical shift due to the electrostatic interactions alone. On addition of Lys-Trp-Gly-Lys OtBu to d-CGCG, the H-5 and H-6 resonances of internal cytosine shift upfield about 0.04-0.07 ppm at 275 K. The upfield shift in external Cytosine are relatively small about 0.01 ppm. Changes in chemical shifts of internal and external Guanine (H-8) are indistinguishable being in the range 0.02-0.11 ppm. The changes in chemical shift of Tryptophan ring protons on binding to oligonucleotide are considerably large, it being typically an upfield shift to 0.18-0.53 ppm at 275 K. The changes in chemical shift of all resonances decrease with temperature. The observations suggest intercalation of Tryptophan ring in d-CGCG. Using the magnetic anisotropy ring current shifts, overlap geometries of Tryptophan ring in d(C-G) and d(G-C) sites of d-CGCG have been proposed. The same has been verified by using Corey-Pauling-Koltun models.
Department of Biosciences and Biotechnology, University of Roorkee, India.
R
R
Barthwal
A
A
Agarwal
S
S
Kukreti
A
A
Mujeeb
D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D009690:Nucleic Acid Conformation; D009838:Oligodeoxyribonucleotides; D009842:Oligopeptides; D011089:Polydeoxyribonucleotides; D011485:Protein Binding; D011487:Protein Conformation; D014364:Tryptophan
D009838:Oligodeoxyribonucleotides; D009842:Oligopeptides; D011089:Polydeoxyribonucleotides; C041173:O-tert-butyl lysyl-tryptophyl-glycyl-lysinate; D014364:Tryptophan