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Shuffling of structural elements in filamentous bacteriophages
1Institute of Molecular Biophysics, Florida State University, Tallahassee 32306-3015, USA.
Proteins
|March 1, 1997
Summary
Filamentous bacteriophage coat proteins share a Ca(2+)-binding motif, suggesting a loop structure in virions. Cation release during assembly may be crucial for filamentous phage formation.
Area of Science:
- Structural biology
- Virology
- Biochemistry
Background:
- Class II filamentous bacteriophage coat proteins possess a conserved 12-amino acid sequence homologous to EF-hand Ca(2+)-binding motifs.
- The Pf3 coat protein exhibits two regions of homology to this sequence, with the Pf1 coat protein's structure in this region being debated.
Purpose of the Study:
- To investigate the structural implications of the conserved sequence in filamentous bacteriophage coat proteins.
- To explore the role of calcium (Ca2+) binding in phage assembly and structure.
Main Methods:
- Comparative sequence analysis of bacteriophage coat proteins.
- Structural modeling and comparison with known Ca(2+)-binding motifs (EF-hand, helix-loop-helix).
Main Results:
- The conserved 12-amino acid sequence's homology to Ca(2+)-binding loops suggests a loop structure in the virion.
- Filamentous phages lack key Ca(2+)-coordinating residues, correlating with weak cation binding.
- Coat proteins may bind cations more effectively in their membrane-bound form than in the virus particle.
Conclusions:
- The conserved sequence likely adopts a loop conformation in filamentous bacteriophages.
- Weak Ca(2+) binding is characteristic of these phages.
- Cation release from the coat protein loop is potentially essential for virus assembly.