Two‐Dimensional Polyacrylamide‐Gel Electrophoresis for Purification of Small RNAs Specified by Virulent Coliphages T4, T5, T7 and BF23

RNAs synthesized in Escherichia coli infected with virulent phages T4, T5, T7 and BF23 were labelled with 32 PO 4 3− after phage infection. [ 32 P]RNAs of low molecular weight were separated by two‐dimensional polyacrylamide gel electrophoresis, in which electrophoresis was carried out in two dimensions at different concentrations of acrylamide. The fractionated RNAs were characterized by RNA‐fingerprint patterns made after T 1 ribonuclease digestion. The two‐dimensional gel of 10%→ 20% acrylamide was suitable for RNA of less than 200 nucleotides, while that of 5%→ 10% was preferred for RNAs of about 150–400 nucleotides. With T4 phage, 16 RNA species were separable on a single slab gel. Among those, 11 were identified as the known RNA species, including eight T4 tRNAs, one tRNA precursor and two non‐tRNA molecules. In the case of T5 and BF23, more than 20 RNA species were separated on a slab gel; 15 or more RNAs were found in the 4‐S RNA region, and several in 5‐S and 6‐S region. The RNA‐fingerprint patterns of many BF23 RNAs were very similar to those of corresponding RNAs of T5. Pseudouridine and ribosylthymidine, minor nucleosides generally present in tRNA, were found in several BF23 4‐S RNAs tested. Possibility of those BF23 4‐S RNAs as tRNAs is discussed. With phage T7, three RNAs were detected, two of which were much smaller than tRNAs.