Features of "All LNA" Duplexes Showing a New Type of Nucleic Acid Geometry.

"Locked nucleic acids" (LNAs) belong to the backbone-modified nucleic acid family. The 2'-O,4'-C-methylene-β-D-ribofuranose nucleotides are used for single or multiple substitutions in RNA molecules and thereby introduce enhanced bio- and thermostability. This renders LNAs powerful tools for diagnostic and therapeutic applications.

The Seryl-tRNA synthetase/tRNASer acceptor stem interface is mediated via a specific network of water molecules.

tRNAs are aminoacylated by the aminoacyl-tRNA synthetases. There are at least 20 natural amino acids, but due to the redundancy of the genetic code, 64 codons on the mRNA. Therefore, there exist tRNA isoacceptors that are aminoacylated with the same amino acid, but differ in their sequence and in the anticodon.

The crystal structure of an 'All Locked' nucleic acid duplex.

'Locked nucleic acids' (LNAs) are known to introduce enhanced bio- and thermostability into natural nucleic acids rendering them powerful tools for diagnostic and therapeutic applications. We present the 1.9 Å X-ray structure of an 'all LNA' duplex containing exclusively modified β-D-2'-O-4'C-methylene ribofuranose nucleotides.

Superposition of two tRNASer acceptor stem crystal structures: comparison of structure, ligands and hydration.

We solved the X-ray structures of two Escherichia coli tRNA(Ser) acceptor stem microhelices. As both tRNAs are aminoacylated by the same seryl-tRNA-synthetase, we performed a comparative structure analysis of both duplexes to investigate the helical conformation, the hydration patterns and magnesium binding sites. It is well accepted, that the hydration of RNA plays an important role in RNA-protein interactions and that the extensive solvent content of the minor groove has a special function in RNA.

Crystallization and preliminary X-ray diffraction data of an LNA 7-mer duplex derived from a ricin aptamer.

Locked nucleic acids (LNAs) are modified nucleic acids which contain a modified sugar such as beta-D-2'-O,4'-C methylene-bridged ribofuranose or other sugar derivatives in LNA analogues. The beta-D-2'-O,4'-C methylene ribofuranose LNAs in particular possess high stability and melting temperatures, which makes them of interest for stabilizing the structure of different nucleic acids. Aptamers, which are DNAs or RNAs targeted against specific ligands, are candidates for substitution with LNAs in order to increase their stability.

Crystallization and X-ray diffraction analysis of an 'all-locked' nucleic acid duplex derived from a tRNA(Ser) microhelix.

Modified nucleic acids are of great interest with respect to their nuclease resistance and enhanced thermostability. In therapeutical and diagnostic applications, such molecules can substitute for labile natural nucleic acids that are targeted against particular diseases or applied in gene therapy. The so-called 'locked nucleic acids' contain modified sugar moieties such as 2'-O,4'-C-methylene-bridged beta-D-ribofuranose and are known to be very stable nucleic acid derivatives.

The 1.2A crystal structure of an E. coli tRNASer)acceptor stem microhelix reveals two magnesium binding sites.

tRNA identity elements assure the correct aminoacylation of tRNAs by the cognate aminoacyl-tRNA synthetases. tRNA(Ser) belongs to the so-called class II system, in which the identity elements are rather simple and are mostly located in the acceptor stem region, in contrast to 'class I', where tRNA determinants are more complex and are located within different regions of the tRNA. The structure of an Escherichia coli tRNA(Ser) acceptor stem microhelix was solved by high resolution X-ray structure analysis.

Crystal structure of the E. coli tRNA(Arg) aminoacyl stem isoacceptor RR-1660 at 2.0 A resolution.

Due to the redundancy of the genetic code there exist six mRNA codons for arginine and several tRNA(Arg) isoacceptors which translate these triplets to protein within the context of the mRNA. The tRNA identity elements assure the correct aminoacylation of the tRNA with the cognate amino acid by the aminoacyl-tRNA-synthetases. In tRNA(Arg), the identity elements consist of the anticodon, parts of the D-loop and the discriminator base.

Crystal structure of the human tRNAGly microhelix isoacceptor G9990 at 1.18A resolution.

The tRNA(Gly)/Glycyl-tRNA synthetase system belongs to the so called 'class II' in which tRNA identity elements consist of relative few and simple motifs, as compared to 'class I' where the tRNA determinants are more complicated and spread over different parts of the tRNA, mostly including the anticodon. The determinants from 'class II' although, are located in the aminoacyl stem and sometimes include the discriminator base. There exist predominant structure differences for the Glycyl-tRNA-synthetases and for the tRNA(Gly) identity elements comparing eucaryotic/archaebacterial and eubacterial systems.

Escherichia coli tRNA(Arg) acceptor-stem isoacceptors: comparative crystallization and preliminary X-ray diffraction analysis.

The aminoacylation of tRNA is a crucial step in cellular protein biosynthesis. Recognition of the cognate tRNA by the correct aminoacyl-tRNA synthetase is ensured by tRNA identity elements. In tRNA(Arg), the identity elements consist of the anticodon, parts of the D-loop and the discriminator base.

X-ray diffraction analysis of a human tRNA(Gly) acceptor-stem microhelix isoacceptor at 1.18 A resolution.

Interest has been focused on comparative X-ray structure analyses of different tRNA(Gly) acceptor-stem helices. tRNA(Gly)/glycyl-tRNA synthetase belongs to the so-called class II system, in which the tRNA identity elements consist of simple and unique determinants that are located in the tRNA acceptor stem and the discriminator base. Comparative structure investigations of tRNA(Gly) microhelices provide insight into the role of tRNA identity elements.