Abstract
The crystal structure of the 92-nucleotide L1-specific fragment of 23S rRNA from Haloarcula marismortui (Hma) has been determined at 3.3 Å resolution. Similar to the corresponding bacterial rRNA fragments, this structure contains joined helix 76-77 topped by an approximately globular structure formed by the residual part of the L1 stalk rRNA. The position of HmaL1 relative to the rRNA was found by its docking to the rRNA fragment using the L1-rRNA complex from Thermus thermophilus as a guide model. In spite of the anomalous negative charge of the halophilic archaeal protein, the conformation of the HmaL1-rRNA interface appeared to be very close to that observed in all known L1-rRNA complexes. The designed structure of the L1 stalk was incorporated into the H. marismortui 50S ribosomal subunit. Comparison of relative positions of L1 stalks in 50S subunits from H. marismortui and T. thermophilus made it possible to reveal the site of inflection of rRNA during the ribosome function.
Highlights
Haloarcula marismortui (Hma) is an extreme halophilic archaeon which is able to grow at salt concentrations close to saturation
The crystal structures of the isolated L1 stalk [11] and 70S ribosomes [5,12,13] from T. thermophilus show that helices and form one helical structure, while the helix consists of two parts (H78a and H78b) that are approximately perpendicular to each other
The 92 nucleotide fragment of 23S rRNA from H. marismortui used in this work contains a part of long helix 76-77 topped by an approximately globular structure formed by the residual part of the L1 stalk rRNA (Figure 1b)
Summary
Haloarcula marismortui (Hma) is an extreme halophilic archaeon which is able to grow at salt concentrations close to saturation. The ribosome of this archaeon functions at 3.5–4.0 M salinity at up to 60 ◦ C. Such conditions usually cause the dissociation of nucleoprotein assemblies and denaturation of isolated proteins. The ribosomal particles obtained from this organism retain their integrity and activity for long periods [1]. The structure of the 50S ribosomal subunit from H. marismortui is the only crystal structure of an archaeal ribosomal particle that has been determined to date [2]. The functionally important mobile L1 protuberance (stalk) is not completely visualized
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