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Biomedical subjects

I Haruna

Publications and source records attributed to I Haruna.

At least 19 recordsLinked to original sources
PubMed1979

Template specificity of Qbeta and SP phage RNA replicases as studied by replication of small variant RNAs.

Template specificity of two RNA-dependent RNA polymerases (Qbeta and SP RNA replicases) was examined using "variant RNAs" as template. Three variant RNAs, one (8S) generated by Qbeta replicase and two (6S and 5.2S) generated by SP replicase, were isolated from the reaction mixtures incubated in the absence of exogenous template RNA. All these RNAs were found to be active as template for both Qbeta and SP replicases, though homologous RNA exhibited activities about three times higher than heterologous RNA with either enzyme, in agreement with the results obtained in phage RNA-dependent reactions. In these reactions, faithful replication of variant RNA was observed, and the amount of RNA synthesized was in a many-fold excess over the template RNA added. We also found that the heterologous RNA-dependent reactions were suppressed by increasing the concentration of salts or decreasing the concentration of substrates. Under such conditions, replication of heterologous variant RNA was almost completely suppressed, while the amount of homologous variant RNA synthesized was only reduced to 50% of that synthesized under the standard conditions. Thus the template specificity of the two RNA replicases seems to be expressed more strictly in these replication systems.

Bacteriophages↗
PubMed1978

Identification of host-derived subunits of phage SP RNA-dependent RNA polymerase (SP replicase).

Phage SP RNA-dependent RNA polymerase (SP replicase) was purified from Escherichia coli infected with RNA phage SP. The enzyme was found to be composed of four non-identical polypeptides, i.e. subunits I, II, III, and IV and molecular weights of 74,000, 69,000, 47,000, and 36,000 daltons, respectively. As in the case of phage Qbeta replicase, the largest polypeptide is identical with the ribosomal protein S1, and subunits III and IV with polypeptide chain elongation factors EF-Tu and EF-ts, respectively.. This is based on the behaviour of the subunits on SDS-polyacrylamide gel electrophoresis, isoelectric focusing and immunological cross-reaction. Subunits I, III, and IV of SP replicase are derived from the host cell, while subunit II is coded by phage RNA genome. The striking coincidence of the composition and entity of the structural components of SP replicase with those of Qbeta replicase may indicate the structural and functional requirements of host-derived polypeptides in RNA replicase. The binding activity of S1 (in 70S ribosome comples) to poly (U) is retained in SP replicase complex. In contrast, the GDP binding activity of EF-Tu is masked in SP replicase. It is concluded that S1 is required functionally whereas EF-Tu.EF-Ts are required structurally in RNA replicase.

Bacterial Proteins↗
PubMed1971

Grouping of RNA phages based on the template specificity of their RNA replicases.

We attempted to apply a new criterion, the template specificity of RNA replicases of Escherichia coli RNA phages, for the grouping of these phages. Based on the template specificity, it was shown that (a) Qbeta, VK, and ST belonged to one group (group III), and SP and FI to another group (group IV), and (b) some similarity existed between groups III and IV. Considering such template specificity in addition to previously reported properties of phage particles, we could separate RNA phages into four major groups (I-IV) with subgroups a, b, and c in group III, and subgroups a and b in group IV.

Coliphages↗