Mutations abolishing the endonuclease activity of bacteriophage lambda terminase lie in two distinct regions of the A gene, one of which may encode a "leucine zipper" DNA-binding domain.
Bacteriophage lambda terminase is a multifunctional enzyme composed of two subunits which are the products of the phage-encoded Nu1 and A genes. The enzyme catalyzes the endonucleolytic cleavage of lambda DNA at a site known as cosN and mediates packaging of the phage DNA into empty heads. This work describes the characterization of mutations within the A gene which lead to the loss of terminase endonuclease activity without affecting the ability of the enzyme to package monomeric mature (cut) lambda DNA. The residues changed by these mutations lie in two distinct regions within the carboxy half of the A protein. One of these regions has sequence homology with a conserved region of DNA polymerases. The other region resembles the "leucine zipper" DNA binding domain (bZIP) found in eukaryotic transcription factors in that both a basic region and leucine heptad-repeat are present. This terminase domain may be involved in the recognition and/or cleavage of cosN.
Davidson
A R
AR
Department of Molecular and Medical Genetics, University of Toronto, Ontario, Canada.
Gold
M
M
D000595:Amino Acid Sequence; D010582:Bacteriophage lambda / Q000235:genetics*; D004252:DNA Mutational Analysis; D019915:DNA Primase; D004259:DNA-Directed DNA Polymerase / Q000235:genetics; D004706:Endodeoxyribonucleases / Q000096:biosynthesis / Q000172:deficiency* / Q000235:genetics*; D005814:Genes, Viral / Q000235:genetics*; D016350:Leucine Zippers / Q000235:genetics; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D011487:Protein Conformation; D012316:RNA Nucleotidyltransferases / Q000235:genetics; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics*; D012689:Sequence Homology, Nucleic Acid
D019915:DNA Primase; D012316:RNA Nucleotidyltransferases; D004259:DNA-Directed DNA Polymerase; D004706:Endodeoxyribonucleases; C030894:terminase