Conformation and dynamics of the Pribnow box region of the self-complementary d(C-G-A-T-T-A-T-A-A-T-C-G) duplex in solution

Abstract

Nuclear magnetic resonance (NMR) has been used to monitor the conformation and dynamics of the d(C1-G2-A3-T4-T5-A6-T6-A5-A4-T3-C2-G1) self-complementary dodecanucleotide duplex (henceforth called Pribnow 12-mer), which contains a TATAAT Pribnow box and a central core of eight dA X dT base pairs. The exchangeable imino and nonexchangeable base protons have been assigned from one-dimensional intra and inter base pair nuclear Overhauser effect (NOE) measurements. Premelting conformational changes are observed at all the dA X dT base pairs in the central octanucleotide core in the Pribnow 12-mer duplex with the duplex to strand transition occurring at 55 degrees C in 0.1 M phosphate solution. The magnitude of the NOE measurements between minor groove H-2 protons of adjacent adenosines demonstrates that the base pairs are propeller twisted with the same handedness as observed in the crystalline state. The thymidine imino proton hydrogen exchange at the dA X dT base pairs has been measured from saturation recovery measurements as a function of temperature. The exchange rates and activation barriers show small variations among the four different dA X dT base pairs in the Pribnow 12-mer duplex.(ABSTRACT TRUNCATED AT 250 WORDS)