| Popis: |
The nucleotide sequences of species I RNA coded for by bacteriophages T2 and T6 have been analyzed using 32-P-labeled material from T2 and T6-infected cultures of Escherichia coli. The T1 and pancreatic ribonuclease digestion products were partially analyzed and the results were compared with nucleotide sequences from T4 species I RNA to obtain a minimum estimate of the number of nucleotide sequence differences among the three species I RNAs. Analysis of fragments obtained by digestion with epsilon-carboxymethyl-lysine-41-pancreatic ribonuclease and with E. coli Q13 S30 crude extract was also performed to provide some additional confirmation for the nucleotide sequences that were derived for the T2 and T6 species I RNAs. T2 species I RNA was found to be different at three positions in the nucleotide sequence, and unlike T4 species I RNA, contained in addition the modified nucleotide, psi, in a region where the proposed secondary structure is identical to the TpsiC-loop of a tRNA. T6 species I RNA was found to contain nucleotide differences from the T4 species I RNA sequence at four positions. The U at position 119 in the sequence appears to be modified to psi only to a small extent. While a biological function for species I RNA is unknown, the fact that there is over 97% homology in the sequences suggests strong evolutionary pressures to retain the nucleotide sequence in the T-even genomes. |
