Alteration of the ATG start codon of the A protein of bacteriophage phi X174 into an ATT codon yields a viable phage indicating that A protein is not essential for phi X174 reproduction.
Bacteriophage phi X174 gene A encodes two proteins: the gene A protein and the smaller A protein, which is synthesized from a translational start signal within the A gene in the same reading frame as the gene A protein. The gene A protein is involved in initiation, elongation and termination of rolling circle DNA replication. The role of the A protein in the life cycle of phi X174, however, is unknown. Using oligonucleotide-directed mutagenesis a viable phi X174 mutant was constructed in which the ATG start codon of the A protein was changed into an ATT codon. This mutant, phi X-4499T, does not synthesize A protein. The burst size of phi X-4499T amounted to 50% of that of wild type phi X174. This indicates that A protein, although advantageous for phage reproduction, is not essential during the life cycle of bacteriophage phi X174.
D010584:Bacteriophage phi X 174 / Q000235:genetics* / Q000502:physiology; D001483:Base Sequence; D003062:Codon / Q000235:genetics*; D004261:DNA Replication; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology; D004706:Endodeoxyribonucleases / Q000235:genetics / Q000502:physiology; D009154:Mutation; D012333:RNA, Messenger / Q000235:genetics*; D014764:Viral Proteins / Q000235:genetics* / Q000502:physiology; D014779:Virus Replication
D003062:Codon; D004268:DNA-Binding Proteins; D012333:RNA, Messenger; D014764:Viral Proteins; D004706:Endodeoxyribonucleases