Isolation and analysis of arc repressor mutants: evidence for an unusual mechanism of DNA binding.
We have isolated 64 different missense mutations at 36 out of 53 residue positions in the Arc repressor of bacteriophage P22. Many of the mutant proteins with substitutions in the C-terminal 40 residues of Arc have reduced intracellular levels and probably have altered structures or stabilities. Mutations in the N-terminal ten residues of Arc cause large decreases in operator DNA binding affinity without affecting the ability of Arc to fold into a stable three-dimensional structure. We argue that these N-terminal residues are important for operator recognition but that they are not part of a conventional helix-turn-helix DNA binding structure. These results suggest that Arc may use a new mechanism for sequence specific DNA binding.
Vershon
A K
AK
Department of Biology, Massachusetts Institute of Technology, Cambridge 02139.
Bowie
J U
JU
Karplus
T M
TM
Sauer
R T
RT
D000595:Amino Acid Sequence; D001435:Bacteriophages / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D004279:DNA, Viral / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005814:Genes, Viral; D008969:Molecular Sequence Data; D009154:Mutation; D009875:Operator Regions, Genetic; D011487:Protein Conformation; D011489:Protein Denaturation; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*; D054334:Viral Regulatory and Accessory Proteins
D004279:DNA, Viral; D004268:DNA-Binding Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins; C016649:phage repressor proteins