A cryptic lysis gene near the start of the Qbeta replicase gene in the +1 frame.
The maturation/lysis (A2) protein encoded by the group B single-stranded RNA bacteriophage Qbeta mediates lysis of host Escherichia coli cells. We found a frameshift mutation in the replicase (beta-subunit) gene of Qbeta cDNA causes cell lysis. The mutant has a single base deletion 73 nucleotides (nt) 3' from the start of the replicase gene with consequent translation termination at a stop codon 129-131 nt further 3'. The 43-amino acid C-terminal part of the 67-amino acid product encoded by what in WT (wild-type) is the +1 frame, is rich in basic amino acids This 67-aa protein can mediate cell lysis whose characteristics indicate that the protein may cause lysis by a different mechanism and via a different target, than that caused by the A2 maturation/lysis protein. Synthesis of a counterpart of the newly discovered lysis product in wild-type phage infection would require a hypothetical ribosomal frameshifting event. The lysis gene of group A RNA phages is also short, 75 codons in MS2, and partially overlaps the first part of their equivalently located replicase gene, raising significant evolutionary implications for the present finding.
Nishihara
Tohru
T
Department of Biochemistry, Kawasaki Medical School, Kurashiki City, Okayama, Japan. tnishihara@ma.0038.net
Morisawa
Hirokazu
H
Ohta
Norihito
N
Atkins
John F
JF
Nishimura
Yukinobu
Y
D017908:Allolevivirus / Q000201:enzymology / Q000235:genetics* / Q000502:physiology; D000595:Amino Acid Sequence; D005075:Biological Evolution; D004926:Escherichia coli / Q000648:ultrastructure / Q000821:virology; D016368:Frameshift Mutation; D008854:Microscopy, Electron; D008858:Microscopy, Phase-Contrast; D008969:Molecular Sequence Data; D010957:Plasmids / Q000648:ultrastructure; D011777:Q beta Replicase / Q000235:genetics*; D017423:Sequence Analysis, RNA; D012965:Sodium Chloride
D012965:Sodium Chloride; D011777:Q beta Replicase