[Stimulation of peptidyltransferase activity of 50S subunits by alcohols]. / Stimuliatsiia peptidiltransferaznoi aktivnosti 50S subchastitsy spirtami.

We have demonstrated that in certain conditions 50S subunits can transfer peptide moiety from peptidyl-tRNA to puromycin in the absence of alcohol. Monovalent cations NH4+ and K+ support this reaction, while Na+ and Li+ are ineffective. Optimal concentration for NH4+ is 1.8 M. Mg2+ ion concentrations above 12 mM are needed as well as an elevated temperature (30 degrees C). Using the alcohol-free puromycin reaction of 50S subunits we show that alcohol activates the peptidyl transferase center, but does not participate in the puromycin reaction. Neither does it change the protein composition of subunits.

[Protein L16 of the Escherichia coli ribosome: possible role in protein biosynthesis]. / Belok L16 ribosomy Escherichia coli: vozmozhnaia rol' v biosinteze belka.

We show that Escherichia coli 50S ribosomal subunits depleted of protein L16 can nevertheless catalyze the transfer of the peptide moiety from fMet-tRNA to puromycin, being, however, unable to use a fragment CACCA-Phe as an acceptor substrate. On the other hand, we found that protein L16 as well as its large fragment (amino acids 10-136) both interact with tRNA in solution (Kd approximately 10(-7) M). Moreover, L16 interacts with CACCA-Phe in solution as well as protects 3' end of tRNA from the enzymatic degradation. We suggest that L16, although not being the peptidyl transferase as such, is involved in the binding of the 3' end cytidines of tRNA into the ribosomal A site.

[Binding of Escherichia coli 50S ribosomal subunit proteins with two large 5S RNA fragments]. / Sviazyvanie belkov 50S subchastitsy ribosomy Escherichia coli s dvumia krupnymi fragmentami 5S RNK.

Two fragments containing sequences from 1-41 nucleotide (small fragment) and from 42-120 nucleotide (large fragment) were isolated from E. coli 5S RNA T1 RNase partial digest. Affinity chromatography of 50S ribosomal proteins on the immobilized 5S RNA fragments revealed the ability of the large fragment to give a complex only with protein L25. The small fragment did not bind ribosomal proteins. The intact and reassociated 5S RNA forms a complex consisting of proteins L5, L18, L25.

[Conformational isomers of rat liver 5S ribosomal RNA]. / Konformatsionnye izomery 5S RNK ribosom pecheni krysy.

The rat liver 5S RNA when denaturated by urea or EDTA, or even without any special treatment, undergoes conformational changes leading to the formation of three electrophoretically distinct isomeres of the molecules with relative mobilities 0.39, 0.44 and 0.47. The band with the slowest mobility corresponds apparently to the native 5S RNA since it is specific for both freshy isolated and renaturated 5S RNA. Moreover, it was found that denaturation of the immobilized 5 S RNA decreases significantly its ability to form a complex with the rat liver 60S ribosomal subunit proteins L6, L7, L8, L18 and L35.