Inovirus (Filamentous Bacteriophage) Strain PF1 Major Coat Protein Assembly

Experimental Data Snapshot

  • Resolution: 3.10 Å

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This is version 1.3 of the entry. See complete history


The Molecular Structure and Structural Transition of the Alpha-Helical Capsid in Filamentous Bacteriophage Pf1

Welsh, L.C.Symmons, M.F.Marvin, D.A.

(2000) Acta Crystallogr D Biol Crystallogr 56: 137

  • DOI: https://doi.org/10.1107/s0907444999015334
  • Primary Citation of Related Structures:  
    1QL1, 1QL2

  • PubMed Abstract: 

    The major coat protein in the capsid of Pf1 filamentous 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 alpha-helix. Since the viral DNA occupies the core of the tubular capsid and appears to make no significant specific interactions with the capsid proteins, the capsid is a simple model system for the study of the static and dynamic properties of alpha-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 first-order structural phase transition. The molecular model of the higher temperature form was refined using improved X-ray fibre diffraction data and new refinement and validation methods. The refinement indicates that the two forms are related by a change in the orientation of the capsid subunits within the virion, without a significant 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.

  • Organizational Affiliation

    Cambridge Centre for Molecular Recognition, Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, England.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
A, B, C
46Primolicivirus Pf1Mutation(s): 0 
Membrane Entity: Yes 
Find proteins for P03621 (Pseudomonas phage Pf1)
Explore P03621 
Go to UniProtKB:  P03621
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP03621
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 3.10 Å
  • Space Group: P 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 1α = 90
b = 1β = 90
c = 1γ = 90
Software Package:
Software NamePurpose
CCP13data reduction
CCP13-FDSCALEdata scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2000-02-07
    Type: Initial release
  • Version 1.1: 2011-05-08
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Version format compliance
  • Version 1.3: 2024-02-14
    Changes: Data collection, Database references, Derived calculations, Refinement description