Posttranscriptional Modifications in Transfer RNA from the Novel Aerobic Hyperthermophile Aeropyrum pernix
Ryan VAN WAGONERa, Eveline BRUENGERa, Pamela F. CRAINa, Norimichi NOMURAb, Yoshihiko SAKOb, and James MCCLOSKEYa
a Department of Medicinal Chemistry, University of Utah, Salt Lake City, Utah 84112, USA
b Laboratory of Marine Microbiology, Kyoto University, Kyoto 606, Japan
Eighty two nucleosides are presently known to occur in tRNA (1), mostly at conserved sequence locations, where they are involved in a variety of functional roles including influence of tertiary structure (2). These modifications, including those known to directly provide thermal stabilization (e.g., 3) are to some extent characteristic of phylogenetic placement of the organism in which they occur. Thus to a certain extent, different modification motifs have evolved between eubacteria and archaea for tRNA stabilization in thermophiles. However knowledge of the structures of posttranscriptionally modified nucleosides and their phylognetic distributions has been relatively narrowly confined to relatively few, well-studied, organisms. It was therefore of interest to examine the tRNA modifications in the recently discovered organism A. pernix, the only known strictly aerobic archaeon growing optimally above 90℃, and representing a new taxon (4). Twenty one modified nucleosides were characterized in enzymatic digests of A. pernix tRNA, including a new tRNA nucleoside, N2,7,2'O-trimethylguanosine, whose structure was confirmed by chemical synthesis. Unusual features of the tRNA are complete absence of the common phylogenetic marker archaeosine, and very low levels of pseudouridine. Several tRNA-stabilizing nucleosides were found, including N4-acety1-2'-O-methylcytidine and N2,N2,O-2-trimethylguanosine, which are unique to the archaea.
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4. Sako, Y., Nomura, N., Uchida, A., Ishida, Y., Morii, H., Koga, Y., Hoaki, T., and Maruyama, T. (1996) Int. J. Sys. Bacteriol., 46, 1070-1077.
