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[Compact particles of double-stranded polyribonucleotides. I. Conditions for the formation of optically active compact double-stranded RNA particles].

The conditions (mol. weight of PEG, ionic strength) of formation of double-stranded RNA (dsRNA) compact particles in water-salt solutions, containing poly(ethylene glycol) (PEG) have been determined. It has been shown, that in solutions of mild ionic strength (approximately 0,3) the compact particles of dsRNA are characterized by an intense positive CD-band (lambda 270 nm), but in solutions of high ionic strength (1,0-1,5)--by intense positive or negative CD-bands (lambda 270 nm). The heating of the solutions of a high ionic strength, containing the compact particles with negative CD-bands is accompanied by the change of sign of CD-band. The same effect is observed in the case of decrease of the ionic strength of the solutions. "Melting" of compact particles as revealed by the CD-method occurs prior to the melting of the secondary structure of dsRNA. These data show, that the intense CD-bands reflect the ordered arrangement of the chromophores of polynucleotide chain in compact particles. The reasons of change of the sign of the CD-bands are discussed.

Circular Dichroism↗
PubMed1979

RNA ligase reaction products in plasmolyzed Escherichia coli cells infected by T4 bacteriophage.

Searching for a physiological role of T4 RNA ligase [polyribonucleotide synthetase (ATP); poly(ribonucleotide):poly(ribonucleotide) ligase (AMP-forming), EC 6.5.1.3] activity, we developed an acellular system of plasmolyzed Escherichia coli cells infected by T4 bacteriophage. Upon incubation of this system with [gamma-32P]ATP, 32P was transferred into a large number of polyribonucleotides, mostly up to 300-400 residues long. The bulk of 32P in the product polyribonucleotides was found in 5'-terminal phosphate groups, suggesting that they originated by a phosphorylation reaction catalyzed by the endogenous polynucleotide kinase (EC 2.7.1.78). Indeed, these products were not seen in an acellular system from uninfected cells, and their amount and complexity increased with the progress of infection. Analysis of the 32P-labeled polyribonucleotide products by gel electrophoresis, either before or after digestion with alkaline phosphatase (EC 3.1.3.1), revealed that a small fraction of the 32P resided in phosphodiester bonds of several tRNA-sized chains. This specific 32P transfer from [gamma-32P]ATP into phosphodiester bonds was apparently catalyzed by successive polynucleotide kinase and RNA ligase reactions. The possible relationship of the 32P transfer to RNA ligase was investigated next by using a system from cells infected with T4 am M69 (an amber mutant deficient in RNA ligase). Transfer of 32P from [gamma-32P]ATP into phosphodiester bonds was not detected in the am M69 system. However, addition of purified RNA ligase to the am M69 system restored the specific 32P transfer. A system from cells infected with T4 psu-b delta 33 (a deletion mutant lacking the entire tRNA region) sustained the specific 32P transfer into tRNA-sized products, indicating that they were not derived from transcripts of T4 tRNA genes. These data may reflect a role of RNA ligase in posttranscriptional conversion of presumably host polyribonucleotides into novel tRNA species during T4 infection.

Adenosine Triphosphate↗