Investigation of the base-pairing structure of the anticodon hairpin from E. coli initiator tRNA by high-resolution nmr

✍ Scribed by K. Lim Wong; David R. Kearns

• Publisher: Wiley (John Wiley & Sons)
• Year: 1974
• Tongue: English
• Weight: 585 KB
• Volume: 13
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.1974.360130212

✦ Synopsis

Abstract

The high‐resolution nmr spectrum of the anticodon hairpin from E. coli tRNA^fMet^ has been obtained at a number of different temperatures. The positions of the resonances from interior Watson‐Crick base pairs are well accounted for (within 0.1 ppm) by a semi‐empirical ring current shift theory, but the terminal base pairs are susceptible to the exact orientation of adjacent bases in single‐stranded regions. From a careful examination of the exact way in which resonances disappear at elevated temperatures, we conclude that melting in the nmr experiments occurs when the lifetime of a base pair is reduced to several milliseconds. On the basis of these experiments we are able to assign an nmr T~m~ to each individual base pair and these should be useful in interpreting the melting behavior of the intact molecule. An “extra” resonance is observed at ∼11.3 ppm and, on the basis of its position and temperature sensitivity, it is tentatively assigned to the ring nitrogen proton of a “protected” U residue in the anticodon loop. A strong preference for stacking of a nonbase‐paired A residue on an adjacent GC base pair is observed even at temperatures in excess of 52°C.