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Bacteriophage P2 and P4 assembly: alternative scaffolding proteins regulate capsid size
O J Marvik1, P Sharma, T Dokland
1Institute of Biology, University of Oslo, Norway.
Virology
|May 1, 1994
Summary
Bacteriophage P2 capsid protein (gpN) self-assembles into two sizes. Scaffolding proteins gpO and gpSid competitively influence capsid size, while gpN processing is self- or host-mediated.
Area of Science:
- Virology
- Molecular Biology
- Structural Biology
Background:
- Bacteriophage P2 capsid protein (gpN) forms icosahedral shells.
- Two capsid sizes (60 nm and 45 nm) are produced.
- Satellite phage P4 utilizes the smaller capsid.
Purpose of the Study:
- Investigate in vivo assembly of P2 capsid protein (gpN).
- Determine the roles of accessory proteins gpO and gpSid in capsid size determination.
- Analyze the proteolytic maturation of gpN.
Main Methods:
- In vivo expression of gpN from a plasmid.
- Co-expression of gpN with P2 scaffolding protein (gpO).
- P4 infection to introduce the sid gene.
Main Results:
- gpN alone forms both 60 nm and 45 nm capsids with low efficiency.
- Co-expression with gpO enhances large (60 nm) particle formation.
- Co-expression with sid gene stimulates small (45 nm) particle assembly.
- gpN undergoes proteolytic maturation independently.
Conclusions:
- gpO and gpSid act antagonistically in P2 capsid size selection.
- gpN processing is likely autocatalytic or host-enzyme mediated.
- gpN has intrinsic assembly capabilities modulated by accessory factors.