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Calcium ion-induced structural changes in bacteriophage phi X174
L L Ilag1, R McKenna, M P Yadav
1Department of Biological Sciences, Purdue University, West Lafayette, IN 47907-1392.
Journal of Molecular Biology
|December 2, 1994
Summary
Calcium ions induce structural changes in bacteriophage phi X174, revealing specific binding sites on capsid proteins. This binding may facilitate glucose interaction, potentially aiding virus attachment to host cells.
Area of Science:
- Structural Biology
- Virology
- Biochemistry
Background:
- Bacteriophage phi X174 is a well-studied virus with a complex capsid structure.
- Understanding viral structural dynamics is crucial for comprehending infection mechanisms.
Purpose of the Study:
- To investigate the structural conformational changes in bacteriophage phi X174 induced by calcium ions (Ca2+).
- To identify and characterize Ca2+ binding sites and their impact on viral structure and potential host interactions.
Main Methods:
- X-ray crystallography was employed to determine the structure of Ca2+-bound bacteriophage phi X174 crystals to 3 Å resolution.
- Detailed analysis of electron density maps to identify Ca2+ coordination and associated protein residues.
Main Results:
- Three distinct Ca2+ binding sites were identified: two associated with the F capsid protein (near 3-fold axes) and one with the G spike protein (near 5-fold axes).
- Ca2+ binding induces conformational changes in the amino-terminal residues of F proteins.
- A potential glucose binding site, ordered only in the presence of Ca2+, was observed near the icosahedral 2-fold axes.
Conclusions:
- Calcium ions play a significant role in stabilizing the bacteriophage phi X174 structure through specific binding interactions.
- The identified Ca2+-dependent glucose binding site suggests a mechanism for initial viral attachment to Escherichia coli through lipopolysaccharides.