Dynamics of tRNA.

Abstract

tRNA, because of its importance in gene translation, is widely studied. To date more than 200 primary structures are known (35), and the crystal structures of several tRNAs have been solved (61, 70, :83, 119, 120, 150, 154). From comparison of the nucleotide sequence aJ).d the tertiary structure of several tRNA species, features common to all tRNAs have emerged. Differences in the tertiary structure oftRNAs have been observed (150-153) that may play a role in their functioning. In general, however, functional aspeCts cannot be deduced from the static picture of atomic coordinates alone. Substantial progress towards a dynamic interpretation of X-ray struc­ tures has been initiated by Frauenfelder et ' al (33) and Artymiuk et al (2), who analyzed mean square displacements, <X2), from atomic equilibrium positions in myoglobin and lysozyme as obtained from temperature factors. Analysis of molecular structures according to these strategies has in the case of proteins already given a most informative picture with regard to conformational variability and flexibility offunctional important domains. We shall focus on these important developments, because they provide the proper background for a discussion of presently available crystallographic data and their relation to kinetics observed by spectroscopic techniques. A detailed description of the dynamic behavior of a molecule like tRNA would require the knowledge of conformational sub states as well as the time evolution of all atomic coordinates. If high intensity X-ray sources and detection techniques with nanosecond and picosecond time resolution were