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Second-site suppressors of a cold-sensitive prohead accessory protein of bacteriophage phi X174
Abstract:
This study describes the isolation of second-site suppressors which correct for the defects associated with cold-sensitive (cs) prohead accessory proteins of bacteriophage phi X174. Five phenotypically different suppressors were isolated. Three of these suppressors confer novel temperature-sensitive (ts) phenotypes. They were unable to complement a ts mutation in gene F which encodes the major coat protein of the phage. All five suppressor mutations confer nucleotide changes in the gene F DNA sequence. These changes define four amino acid sites in the gene F protein. Three suppressor mutations placed into an otherwise wild-type background display a cold resistant phenotype in liquid culture infections when compared to a wild-type phi X174 control.
Insights
Researchers identified suppressors that fix defects in bacteriophage phi X174 prohead proteins. These suppressors alter the major coat protein gene F, impacting phage growth at different temperatures.
Area of Science:
- Molecular Biology
- Virology
- Genetics
Background:
- Bacteriophage phi X174 requires specific prohead accessory proteins for proper assembly.
- Cold-sensitive (cs) mutations in these proteins cause defects in phage production at low temperatures.
- Understanding these defects is crucial for deciphering phage assembly mechanisms.
Purpose of the Study:
- To isolate and characterize second-site suppressors of cold-sensitive mutations in bacteriophage phi X174 prohead accessory proteins.
- To investigate the genetic basis and phenotypic consequences of these suppressors.
- To identify the specific gene and protein alterations responsible for suppression.
Main Methods:
- Isolation of second-site suppressors using phenotypic screening.
- Complementation analysis to assess the interaction of suppressors with known mutations.
- DNA sequencing to identify nucleotide changes in suppressor mutations.
- Phenotypic characterization of suppressor mutations in wild-type and mutant backgrounds.
Main Results:
- Five distinct suppressors of cold-sensitive prohead accessory protein defects were isolated.
- Three suppressors exhibited novel temperature-sensitive (ts) phenotypes.
- All five suppressor mutations mapped to gene F, encoding the major coat protein.
- Suppressor mutations resulted in nucleotide changes within gene F, defining four amino acid sites.
- Three suppressor mutations conferred a cold-resistant phenotype in liquid culture infections compared to wild-type phi X174.
Conclusions:
- Second-site suppressors can functionally correct defects in bacteriophage phi X174 prohead accessory proteins.
- Mutations in the major coat protein gene F can suppress defects in prohead assembly.
- These findings provide insights into the complex interactions between phage proteins during assembly and the genetic basis of phage assembly regulation.