Mutational analysis of the activator of late transcription, Alt, in the lactococcal bacteriophage TP901-1.
An activator protein, Alt, synthesized during the early state of lytic infection is required for transcription of the late operon in the lactococcal phage TP901-1. In order to identify amino acid residues in the Alt protein required for activation of the TP901-1 late promoter, P(late), hydroxylamine mutagenesis was performed, resulting in almost saturating mutagenesis of alt. Twenty-three different non-functional alt alleles containing one, and in one case two amino acid exchanges were isolated and analyzed. Eight of the twenty-three mutant proteins were still able to activate the P(late) promoter to some extent. Our results show that alt encodes a protein of 16.7 kDa and that the last fourteen amino acids in the C-terminal part of the protein are required for activation of the P(late) promoter. By combining sequence analysis with experimental data we suggest that the C-terminal half of the Alt protein contains a helix-turn-helix-like motif involved in DNA binding. We also propose that the C-terminal half of the Alt protein may be involved in interactions with the bacterial RNA polymerase, whereas the N-terminal half of the protein is proposed to be important for the overall protein structure.
Pedersen
M
M
Technical University of Denmark, Biocentrum-DTU, Lyngby, Denmark. mpe@biocentrum.dtu.dk
Hammer
K
K
D000483:Alleles; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D004252:DNA Mutational Analysis; D005814:Genes, Viral; D019077:Helix-Turn-Helix Motifs; D013294:Lactococcus lactis / Q000235:genetics / Q000821:virology*; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014764:Viral Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
D014764:Viral Proteins