Influence of Temperature on tRNA Modification in Archaea: Methanococcoides burtonii (Optimum Growth Temperature [ T opt ], 23°C) and Stetteria hydrogenophila ( T opt , 95°C)
| Autor: | Rebecca Guymon, Julianne Lim, James A. McCloskey, Michael Thomm, Pamela F. Crain, Ricardo Cavicchioli, Kathleen R. Noon |
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| Rok vydání: | 2003 |
| Předmět: | |
| Zdroj: | Journal of Bacteriology. 185:5483-5490 |
| ISSN: | 1098-5530 0021-9193 |
| DOI: | 10.1128/jb.185.18.5483-5490.2003 |
| Popis: | The posttranscriptional processing of tRNA produces a diverse wealth of modified nucleotides (29, 30, 41), most of which occur at conserved RNA sequence locations in all three phylogenetic domains (4, 45). Many of the functional roles of these modifications, in addition to other factors, such as G-C and metal ion content, are associated with their influence on secondary and tertiary structures in RNA (1, 14, 43). Thus, RNA modifications offer an important means of mediation of RNA structure across the entire temperature range of natural habitats for microorganisms: in low-temperature organisms, a degree of conformational flexibility in tRNA must be maintained during translation, while in the case of thermophiles, protection against environmental temperatures which may exceed the melting point of unmodified base-paired stems is required (27, 50). For example, it has been shown with increases in growth temperature for a single species (2, 27, 51) or through comparison of closely related organisms growing optimally at different temperatures (32) that selected stabilizing tRNA modifications are associated with increased culture temperature. By contrast, in bacterial psychrophiles, low levels of modification have been reported, with the exception of dihydrouridine (10), a modified tRNA nucleoside which is associated with enhancement and maintenance of molecular flexibility at low temperatures (12). From a phylogenetic perspective, it is interesting that the nucleoside structural motifs used for RNA stabilization at higher temperatures are known to be different in bacterial thermophiles (13, 24) and archaeal thermophiles (17), but tRNA modifications in low-temperature archaea have not previously been examined. We report here a detailed study of the identities and levels of nucleoside modifications in unfractionated tRNA from the psychrotolerant archaeon Methanococcoides burtonii (20). Cultures were grown at 23°C (the optimum growth temperature) and at 4°C (closer to the natural habitat temperature of 1 to 2°C [20]) in order to examine the overall level of tRNA modifications in comparison with that in bacteria, as well as recently studied mesophilic and thermophilic methanococci (32), and to assess the influence of a significant reduction in culture temperature upon modification. For contrast within the archaeal domain, we examined tRNA from the hyperthermophile Stetteria hydrogenophila (25) cultured at 93°C, near the growth optimum of 95°C. In both cases nucleoside modifications were measured by analysis of total enzymatic digests of tRNA using combined LC/MS, a definitive method for structural identification of RNA nucleoside modifications (7, 39). |
| Databáze: | OpenAIRE |
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