Related Experiment Videos
Mutational analysis of the bacteriophage P4 capsid-size-determining gene
O Nilssen1, E W Six, M G Sunshine
1Laboratory of Microbial Gene Technology, NLVF, Norway. Oivindn@fagmed.uit.no
Virology
|May 15, 1996
Summary
Satellite phage P4 redirects helper phage P2 assembly to produce smaller capsids, a process controlled by the P4 Sid protein. Mutational analysis revealed distinct functional domains within the Sid polypeptide, crucial for capsid size determination.
Area of Science:
- Bacteriophage biology
- Molecular genetics
- Structural biology
Background:
- Satellite phage P4 relies on helper phage P2 for lytic development.
- P4 modifies P2's morphopoietic pathway to produce smaller capsids (45 nm) compared to P2 (60 nm).
- The P4-specified capsid size is determined by the 27-kDa Sid protein.
Purpose of the Study:
- To investigate the capsid size-determining function of the P4 Sid protein.
- To perform a mutational analysis of the P4 sid gene.
Main Methods:
- Utilized a P4-derived genome (P461) packaging exclusively into large, P2-sized capsids to select for P4 Sid- mutants.
- Characterized 25 P4 Sid- mutants using DNA sequencing.
- Identified mutations including base pair substitutions and deletions.
Main Results:
- 25 P4 Sid- mutants were identified and sequenced.
- 10 mutants had base pair substitutions, and 15 had deletions.
- Mutations were clustered in specific regions of the sid gene.
Conclusions:
- The Sid polypeptide possesses at least three distinct functional domains.
- These domains are critical for regulating P4 capsid size determination.
- The findings provide insights into the molecular mechanisms of phage capsid assembly.