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Subunit conformational changes accompanying bacteriophage P22 capsid maturation
P E Prevelige1, D Thomas, K L Aubrey
1Department of Biology, Massachusetts Institute of Technology, Cambridge 02139.
Biochemistry
|January 19, 1993
Summary
Viral capsid transformation involves significant protein conformational changes without subunit dissociation. Raman spectroscopy reveals minor secondary structure alterations but substantial side-chain modifications during DNA packaging in bacteriophages.
Area of Science:
- Structural biology
- Virology
- Biochemistry
Background:
- Bacteriophage DNA packaging involves procapsid to mature capsid transformation.
- This process requires lattice expansion and scaffolding subunit release.
- Capsid transformation involves significant changes in subunit environment without dissociation.
Purpose of the Study:
- To investigate the conformational changes in coat proteins during bacteriophage capsid transformation.
- To understand the relationship between DNA packaging, shell expansion, and subunit conformation.
Main Methods:
- Three-dimensional structural analysis of procapsid and mature phage lattices.
- Raman spectroscopy to analyze coat protein secondary structure and side-chain environments.
Main Results:
- Capsid transformation involves transitions between stable subunit conformations.
- Raman spectroscopy detected minor changes in alpha-helix and beta-sheet content (2.0 +/- 0.4% more alpha-helix in procapsids).
- Significant alterations were observed in side chains of tyrosines, tryptophans, phenylalanines, and aliphatics.
Conclusions:
- Bacteriophage procapsid expansion is driven by relative motion of coat subunit domains with minimal secondary structure changes.
- Hinge-bending conformational transitions likely couple ATP-dependent DNA condensation with shell expansion.