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Terminating a macromolecular helix. Structural model for the minor proteins of bacteriophage M13
1Department of Physics, Boston University, MA 02215.
Abstract:
Analysis of the results of X-ray diffraction, electron microscopy and s sequence studies of filamentous bacteriophage M13 are used to construct structural models for the minor proteins gp7 and gp9 at the end of the virus assembled first, and a portion of gp6 at the end of the virus that binds host. Comparison of the sequence of the major coat protein, gp8, with those of gp7, gp9 and gp6 indicates that significant portions of these three proteins have sequences similar to that of gp8. Assuming that sequence similarity is indicative of structural similarity, gp7, gp9 and portions of gp6 are modeled based on what is known about the structure of gp8. These molecular models are analyzed to predict the packing of the minor proteins with the terminal gp8 proteins (the last gp8 proteins at either end of the helix). This analysis indicates that the gp8 proteins integrated into the virus first may have a structure distinct from those in the body of the virus particle. The gp8 proteins at the end assembled last appear to have a conformation very similar to that of the integral coat proteins. These models place specific constraints on models for the process of viral assembly.
Insights
Structural models of bacteriophage M13 minor proteins reveal insights into viral assembly. Sequence similarities suggest structural similarities, impacting how proteins pack and potentially altering the structure of early viral components.
Area of Science:
- Structural biology
- Virology
- Molecular genetics
Background:
- Filamentous bacteriophage M13 is a model system for studying viral assembly.
- Understanding the structure of viral proteins is crucial for elucidating assembly mechanisms.
Purpose of the Study:
- To construct structural models for minor proteins (gp7, gp9, gp6) of bacteriophage M13.
- To predict the packing of minor proteins with terminal major coat proteins (gp8).
Main Methods:
- X-ray diffraction
- Electron microscopy
- Sequence analysis
- Comparative sequence analysis
- Molecular modeling
Main Results:
- Structural models for minor proteins gp7, gp9, and a portion of gp6 were developed.
- Sequence similarity between minor proteins and major coat protein gp8 suggests structural similarity.
- Analysis predicts distinct structures for early gp8 proteins compared to integral coat proteins.
Conclusions:
- The proposed molecular models provide constraints on existing models of bacteriophage M13 assembly.
- The structure of gp8 proteins may vary depending on their position and timing of incorporation during assembly.