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[Structure of virions of the M13 phage containing chimeric B-protein molecules]
Abstract:
We have studied the virion structure of M13 strains (M13B1, M13BOM1, M13BOM2, M13BOL1) with chimeric variants of B-protein. Data concerning the spatial structure of chimeric B-protein molecules and their interaction with intraphage DNA were obtained. The phage contour lengths were measured under electron microscope and the DNA/protein ratios were obtained by spectrophotometry. These data testified that the insertion of foreign peptide affected neither DNA packaging nor the compactness of molecular arrangement of proteins in the virion. By linear dichroism and fluorescence spectra of phages it was determined, that the insert can influence the polarity of amino acid environment and the orientation of amino acids in the B-protein central part. It was shown by quenching of phage fluorescence by KI that the inward or outward amino acids location in the capsid is invariable. The carboxyl residues have been titrated in the phage strains by Auramine O. It was shown that there is no correlation between the number of the titrated carboxyl groups and the number of the carboxyl groups as a whole.
Insights
Chimeric B-protein variants in M13 bacteriophage did not alter DNA packaging or virion compactness. However, inserts influenced the amino acid environment and orientation within the B-protein, affecting phage structure.
Area of Science:
- Molecular biology
- Structural biology
- Virology
Context:
- The M13 bacteriophage is a well-characterized model system for studying viral structure and DNA packaging.
- Understanding the role of the B-protein in virion assembly and DNA interaction is crucial for viral biology.
- Chimeric protein variants allow for the investigation of specific functional domains and their impact on overall structure.
Purpose:
- To investigate the structural and functional consequences of incorporating foreign peptides into the M13 bacteriophage B-protein.
- To determine how modifications in the B-protein affect DNA packaging, virion compactness, and the internal environment of the phage.
- To elucidate the spatial arrangement and orientation of amino acids within the B-protein and their interaction with phage DNA.
Summary:
- Studies on M13 bacteriophage strains with chimeric B-protein variants revealed that foreign peptide insertions did not disrupt DNA packaging or virion protein arrangement.
- Analysis using electron microscopy, spectrophotometry, linear dichroism, and fluorescence spectroscopy indicated that inserts can alter the amino acid environment and orientation in the B-protein's core.
- Carboxyl group titration showed no correlation between titrated groups and total carboxyl groups, suggesting specific surface or internal accessibility.
Impact:
- This research provides insights into the structural plasticity of viral proteins and their adaptability to foreign peptide insertions.
- Findings contribute to a deeper understanding of M13 bacteriophage assembly and the determinants of virion stability.
- The study highlights how specific amino acid modifications can subtly alter the biophysical properties of viral capsids without compromising essential functions like DNA packaging.