[Ribosomal antibiotics].

In spite of decades of research, our understanding of the principles of antibiotic binding to the ribosome and the mechanisms of drug action remains only fragmentary. Recent progress in biochemical and genetic studies of some "old" and new antibiotics and the availability of high-resolution structures of the ribosome subunits allows mapping the antibiotic-binding sites at atomic resolution. In this review, interaction of three groups of antibiotics with the ribosome and the mechanisms of the drug action are discussed, considering the data used to map the binding sites of the new macrolide derivatives, ketolides, a novel clinically important antibiotic linezolid, and a still experimental drug evernimicin.

[Instability of the halophilic archaebacteria genome].

The phenomenon of high genetic variability in the extremely halophilic archaebacterium Hb. salinarium is reviewed. The role of IS elements and homologous recombination in frequent genetic rearrangements in this organism is discussed.

[3'terminal nucleotide sequence of barley stripe mosaic virus RNA].

Barley stripe mosaic virus (BSMV) is a representative of the hordeiviruses which has a functionally fragmented RNA genom. 3'-terminal nucleotide sequence of the noncoding region of BSMV RNA 2 has been determined. This region contains the internal olygo(A) sequence (n = 21) and the tyrosine accepting tRNA-like structure at 3'-extreme end.

[Cleavage of tRNA and rRNA at 7-methylguanine in the presence of methylated carrier RNA].

A method of site-specific cleavage of some tRNAs and rRNAs at the 7-methylguanine residue is described. After reduction of 7-methylguanine by sodium borohydride treatment in the presence of the exogenous carrier RNA methylated statistically by dimethylsulfate the polynucleotide chain is cut at the modified residue by aniline. It was shown that the previously used procedure which did not involve a methylated carrier RNA is not applicable for splitting rRNAs or low concentrations of tRNAs.