Two Forms of Pf1 Inovirus: X-Ray Diffraction Studies on a Structural Phase Transition and a Calculated Libration Normal Mode of the Asymmetric Unit

The major coat protein in the capsid of Pf1 ®lamentous bacteriophage (Inovirus) forms a helical assembly of about 7000 identical protein subunits, each of which contains 46 amino-acid residues and can be closely approximated by a single gently curved -helix. Since the viral DNA occupies the core of the tubular capsid and appears to make no signi®cant speci®c interactions with the capsid proteins, the capsid is a simple model system for the study of the static and dynamic properties of -helix assembly. The capsid undergoes a reversible temperature-induced structural transition at about 283 K between two slightly different helix forms. The two forms can coexist without an intermediate state, consistent with a ®rst-order structural phase transition. The molecular model of the higher temperature form was re®ned using improved X-ray ®bre diffraction data and new re®nement and validation methods. The re®nement indicates that the two forms are related by a change in the orientation of the capsid subunits within the virion, without a signi®cant change in local conformation of the subunits. On the higher temperature diffraction pattern there is a region of observed intensity that is not consistent with a simple helix of identical subunits; it is proposed that the structure involves groups of three subunits which each have a slightly different orientation within the group. The grouping of subunits suggests that a change in subunit libration frequency could be the basis of the Pf1 structural transition; calculations from the model are used to explore this idea.

show abstract

The molecular structure and structural transition of the α-helical capsid in filamentous bacteriophage Pf1

Welsh

Symmons

Marvin

2000

Acta Crystallogr D Biol Cryst

View full text Add to dashboard Cite

show abstract

scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.

Contact Info

hi@scite.ai

10624 S. Eastern Ave., Ste. A-614

Henderson, NV 89052, USA

Blog Terms and Conditions API Terms Privacy Policy Contact Cookie Preferences Do Not Sell or Share My Personal Information

Made with 💙 for researchers

Part of the Research Solutions Family.

Two Forms of Pf1 Inovirus: X-Ray Diffraction Studies on a Structural Phase Transition and a Calculated Libration Normal Mode of the Asymmetric Unit

Cited by 1 publication

References 32 publications

The molecular structure and structural transition of the α-helical capsid in filamentous bacteriophage Pf1

The molecular structure and structural transition of the α-helical capsid in filamentous bacteriophage Pf1

Contact Info

Product

Resources

About