Crystal Structure of Rhagium inquisitor Antifreeze Protein

Experimental Data Snapshot

  • Resolution: 1.15 Å
  • R-Value Free: 0.161 
  • R-Value Work: 0.137 
  • R-Value Observed: 0.138 

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This is version 1.3 of the entry. See complete history


Crystal structure of an insect antifreeze protein and its implications for ice binding.

Hakim, A.Nguyen, J.B.Basu, K.Zhu, D.F.Thakral, D.Davies, P.L.Isaacs, F.J.Modis, Y.Meng, W.

(2013) J Biol Chem 288: 12295-12304

  • DOI: https://doi.org/10.1074/jbc.M113.450973
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 

    Antifreeze proteins (AFPs) help some organisms resist freezing by binding to ice crystals and inhibiting their growth. The molecular basis for how these proteins recognize and bind ice is not well understood. The longhorn beetle Rhagium inquisitor can supercool to below -25 °C, in part by synthesizing the most potent antifreeze protein studied thus far (RiAFP). We report the crystal structure of the 13-kDa RiAFP, determined at 1.21 Å resolution using direct methods. The structure, which contains 1,914 nonhydrogen protein atoms in the asymmetric unit, is the largest determined ab initio without heavy atoms. It reveals a compressed β-solenoid fold in which the top and bottom sheets are held together by a silk-like interdigitation of short side chains. RiAFP is perhaps the most regular structure yet observed. It is a second independently evolved AFP type in beetles. The two beetle AFPs have in common an extremely flat ice-binding surface comprising regular outward-projecting parallel arrays of threonine residues. The more active, wider RiAFP has four (rather than two) of these arrays between which the crystal structure shows the presence of ice-like waters. Molecular dynamics simulations independently reproduce the locations of these ordered crystallographic waters and predict additional waters that together provide an extensive view of the AFP interaction with ice. By matching several planes of hexagonal ice, these waters may help freeze the AFP to the ice surface, thus providing the molecular basis of ice binding.

  • Organizational Affiliation

    Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520, USA.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Antifreeze protein
A, B
143Rhagium inquisitorMutation(s): 0 
Gene Names: afp-h4
Find proteins for E5LR38 (Rhagium inquisitor)
Explore E5LR38 
Go to UniProtKB:  E5LR38
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupE5LR38
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 1.15 Å
  • R-Value Free: 0.161 
  • R-Value Work: 0.137 
  • R-Value Observed: 0.138 
  • Space Group: P 31 2 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 46.46α = 90
b = 46.46β = 90
c = 193.21γ = 120
Software Package:
Software NamePurpose
PDB_EXTRACTdata extraction
HKL-3000data collection
XDSdata reduction
XSCALEdata scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2013-03-13
    Type: Initial release
  • Version 1.1: 2013-07-31
    Changes: Database references
  • Version 1.2: 2017-11-15
    Changes: Refinement description
  • Version 1.3: 2019-07-17
    Changes: Data collection, Refinement description