Analysis of a mutation affecting the specificity domain for prohead binding of the bacteriophage lambda terminase.
Genetic studies have identified a specificity domain for prohead binding in the C-terminal 32 amino acids of gpA, the large subunit of bacteriophage lambda terminase (S. Frackman, D. A. Siegele, and M. Feiss, J. Mol. Biol. 180:283-300, 1984). In the present work, an amber mutation, Aam42, in the fifth-to-last codon of the A gene was found to be lethal in nonsuppressing hosts. The mutation, expected to generate gpA lacking the last five amino acids, caused the production of a terminase that cut cos efficiently both in vivo and in vitro but was defective in DNA packaging. lambda Aam42 lysates contained unused proheads, consistent with a defect in prohead binding. Aam42 terminase was more strongly dependent than wild-type terminase on gpFI, the catalyst of prohead binding. Like wild-type terminase, Aam42 terminase did not cut cos in vivo when prohead assembly was blocked by a mutation in one of the genes encoding the prohead.
Sippy
J
J
Department of Microbiology, University of Iowa, Iowa City 52242.
Feiss
M
M
D010582:Bacteriophage lambda / Q000235:genetics*; D001483:Base Sequence; D003062:Codon; D004706:Endodeoxyribonucleases / Q000235:genetics*; D015967:Gene Expression Regulation, Viral; D005816:Genetic Complementation Test; D008954:Models, Biological; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation / Q000235:genetics*; D014779:Virus Replication / Q000235:genetics*
D003062:Codon; D004706:Endodeoxyribonucleases; C030894:terminase