Deletion analysis of Qbeta replicase. Participation of the carboxyl-terminal region of the beta-subunit protein in template recognition.
We have analyzed one of the functional domains of Qbeta replicase, an RNA-dependent RNA polymerase of RNA coliphage Qbeta. Deletion mapping analysis of the carboxyl-terminal region of the beta-subunit protein revealed that the terminal 18 amino acid residues (positions 571-588) are dispensable for the replicase reaction. Subsequent deletions up to the Ala-565 residue reduced the RNA polymerizing activity of the replicase in vivo but increased it in vitro. The mutant replicases with enhanced in vitro RNA polymerizing activity were found to have relaxed template specificity for ribosomal RNAs and cellular RNAs as well as Qbeta RNA. Deletions beyond the Ile-564 residue abolished both the RNA polymerizing activity and the binding ability to midivariant (MDV)-poly(+) RNA, a derivative of a natural template for Qbeta replicase, MDV-1 RNA. These results suggest that the carboxyl-terminal part of the beta-subunit participates in RNA recognition of Qbeta replicase.
Inokuchi
Y
Y
Department of Biosciences, Teikyo University, 1-1 Toyosatodai, Utsunomiya-shi, Tochigi 320, Japan.
Kajitani
M
M
D000595:Amino Acid Sequence; D001435:Bacteriophages / Q000254:growth & development; D015152:Blotting, Northern; D008969:Molecular Sequence Data; D010957:Plasmids; D011777:Q beta Replicase / Q000378:metabolism*; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D013698:Templates, Genetic
D011777:Q beta Replicase