[Peptidyltransferase center of ribosomes. II. Effect of temperature on the activity of model peptide donors and a study of oligopeptide formation in a matrix-free system with ribosomes]. / Peptidiltransferaznyi tsentr ribosom. II. Vliianie temperatury na aktivnost' model'nykh donorov peptida i issledovanie obrazovaniia oligopeptidov v bezmatrichnoi sisteme s ribosomami.

The reaction of 3'(2')-O-(N-formylmethionyl)-adenosine 5'-phosphate with Phe-tRNA or CACCA-Phe catalysed with E. coli MRE-600 ribosomes and stimulated with cytidine 5'-phosphate was investigated. It was shown that the reaction with Phe-tRNA was stimulated within 2--3 times when the temperature has been raised from 0 to 40 degrees. On the contrary when the peptide acceptor was CACCA-Phe the yield of peptides synthesis dropped 5 times and more under the same conditions. Similar temperature influence was observed in the reaction with 50S subunits. The inhibition of peptide bond formation with pA and CpA at 0 degrees was achieved up to 80--90% but it was very low at 40 degrees. The synthesis of tri- and tetrapeptides was observed when the reaction of 3'(2')-O-(N-formylmethionyl)-adenosine 5'-phosphate was carried out either with Phe-tRNA or with CACCA-Phe.

[Peptidyl transferase center of ribosomes. I. Difference in the substrate specificity of the acceptor and donor portions]. / Peptidiltransferaznyi tsentr ribosom. I. Razlichie v substratnoi spetsifichnosti aktseptornogo i donornogo uchastkov.

Some model substrates of the peptidyl transferase centre of E. coli MRE-600 ribosomes were synthesised and tested in a cell-free system without a template. In these substances the nucleic bases were linked covalently with the ribose residue or had a limited rotation about the glycosidic bond. 3'(2')-O-(N-formylmethionyl)-8-bromoadenosine 5'-phosphate and 3'(2')-O-phenylalanyl-8,5'-anhydro-8-mercaptoadenosine were shown to possess a high peptide donor and acceptor activity correspondingly. Contrary to that 3'(2')-O-phenylalanyl-8-bromoadenosine was practically inactive as a peptide acceptor and 3'(2')-O-(N-formylmethionyl)-8,5'-anhydro-8-mercaptoadenosine had no peptide donor activity at all. PMR and CD spectra of the compounds synthesised were investigated. The significance of conformation of the model substrates on their activity is discussed.

[Fragment reaction catalyzed by E. coli ribosomes]. / Issledovanie fragmentnoi reaktsii, kataliziruemoi ribosomami E. coli.

It has been shown that 50S subunits of E. coli MRE-600 ribosomes catalyze the reaction of N-(formyl)-methionyl ester of adenosine 5'-phosphate acting as peptide donor, with Phe-tRNA or CACCA-Phe serving as a peptide acceptor. The reaction is stimulated by cytidine 5'phosphate and inhibited by lincomycin, puromycin and chloramphenicol. The obtained results show that the structure of the donor site of peptidyltransferase is completely assembled on the 50S subunit and 30S subunit is not required for its formation.

Catalysis of the peptide bond formation by 50 S subunits of E. coli ribosomes with N-(formyl) methionine ester of adenylic acid as peptide donor.

50 S subunits of E. coli ribosomes catalyze the reaction of the 2'(3')-N-(formyl) methionine ester of adenosine 5'-phosphate and Phe-tRNA resulting in peptide bond synthesis. Cytidine 5'-phosphate stimulates this process on 50 S ribosomal subunits as well as on intact ribosomes. The obtained data show that the areas of the peptidyltransferase donor site which binds the 3'-terminal fragment of peptidyl-tRNA possess completely formed structures on 50 S ribosomal subunits.

[Donor site of E. coli ribosomal peptidyltransferase]. / Issledovanie donornogo uchastka peptidiltransferazy ribosom E. coli.

The mechanism of 5'-cytidilic acid stimulation of the reaction between 2'(3')-O-formylmethionine ester of 5'-adenylic acid and phenylalanyl-tRNA catalyzed by E. coli ribosomes has been studied. It has been shown that cytidilic acid binds to the donor site of the peptidyltransferase in the area which is usually occupied by the second nucleotide residue of the peptidyl-tRNA 3'-end. After the binding cytidilic acid stimulates effectively the donor activity of formylmethionine ester of adenylic acid. A number of compounds have been tested as possible stimulants. Both the chemical nature of stimulant and its conformation are important for the stimulating action. A hypothetic scheme is suggested explaining possible causative factors of peptidyl-tRNA translocation from the acceptor site to the donor site after peptide bond formation.