A V Semerjian | PubMed Health

PubMed1991

Bacteriophage P22 accessory recombination function.

The accessory recombination function (arf) gene of bacteriophage P22 is located immediately upstream of the essential recombination function (erf) gene. Three mutant alleles of arf were constructed and installed in P22 in place of the wild-type allele: an out-of-frame internal deletion, an in-frame internal deletion, and an amber mutation. The deletion mutant phages are partially defective in homologous recombination and plaque formation in wild-type and recA hosts; their defects are more severe in recB and recA recB hosts. The amber mutant phage exhibits the same growth phenotypes in nonsuppressing hosts, but not in an amber-suppressor host. Plasmids that express arf complement the growth defect of arf- phages. These plasmids stimulate erf-mediated recombination; they were also found to cause a small stimulation of recA-recBCD-mediated homologous recombination of phage lambda.

Amino Acid Sequence↗

PubMed1989

Genetic structure of the bacteriophage P22 PL operon.

The sequence of 1416 base-pairs of the P22 PL operon was determined, linking a continuous sequence from PL through abc2. P22 mutants bearing deletions in the sequenced region were constructed and tested for their phenotypes. Plasmids were constructed to express PL operon genes singly and in combination from Plac UV5. Two previously known genes, 17 and c3, are located within this sequence. In addition, three new genes have been identified: ral, kil and arf. Genes ral and c3 are homologous, as well as functionally analogous, to lambda ral and cIII, respectively. P22 kil, like lambda kil, kills the host cell when it is expressed. The two kil genes, although analogous in cell killing and map location, have no apparent sequence homology. The functions of the P22 and lambda kil genes are unknown; however, P22 kil is essential for lytic growth in the absence of abc. Gene arf (accessory recombination function) is located just upstream from erf; it is essential for P22 growth in the absence of kil or other genes upstream in PL. The growth defect of P22 bearing a deletion that removes arf is complemented by expression of either arf or the lambda red genes from plasmids. Sequences that include the stop codon for gene 17 may form a small stem-loop structure and are nearly identical to lambda sequences that contain the stop codon for ssb, which is near lambda tL 2b. Plasmids that include the P22 structure negatively regulate kil gene expression in cis.

Amino Acid Sequence↗