Altered 3'-terminal RNA structure in phage Qbeta adapted to host factor-less Escherichia coli.

摘要: The RNA phage Qbeta requires for the replication of its genome an binding protein called host factor or Hfq protein. Our previous results suggested that this mediates access replicase to 3'-end plus strand RNA. Here we report evolutionary experiment in which was adapted Escherichia coli Q13 strain with inactivated (hfq) gene. This initially produced at a titer approximately 10,000-fold lower than wild-type and minute plaque morphology, but after 12 growth cycles, size had evolved levels near those host. RNAs isolated from mutants were efficient templates without vitro. Electron microscopy showed mutant RNAs, contrast RNA, efficiently interacted absence factor. same set four mutations 3'-terminal third found several independently clones. One mutation disrupts base pairing CCCOH sequence, suggesting stimulates activity template by melting out 3'-end.