Structure of ranaspumin-2, a surfactant protein from the foam nests of a tropical frog

Experimental Data Snapshot

  • Method: SOLUTION NMR
  • Conformers Calculated: 100 
  • Conformers Submitted: 25 
  • Selection Criteria: LEAST RESTRAINT VIOLATION 

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Ranaspumin-2: Structure and Function of a Surfactant Protein from the Foam Nests of a Tropical Frog.

Mackenzie, C.D.Smith, B.O.Meister, A.Blume, A.Zhao, X.Lu, J.R.Kennedy, M.W.Cooper, A.

(2009) Biophys J 96: 4984

  • DOI: https://doi.org/10.1016/j.bpj.2009.03.044
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 

    Ranaspumin-2 (Rsn-2) is a monomeric, 11 kDa surfactant protein identified as one of the major foam nest components of the túngara frog (Engystomops pustulosus), with an amino acid sequence unlike any other protein described so far. We report here on its structure in solution as determined by high-resolution NMR analysis, together with investigations of its conformation and packing at the air-water interface using a combination of infrared and neutron reflectivity techniques. Despite the lack of any significant sequence similarity, Rsn-2 in solution adopts a compact globular fold characteristic of the cystatin family, comprising a single helix over a four-stranded sheet, in a motif not previously associated with surfactant activity. The NMR structure of Rsn-2 shows no obvious amphiphilicity that might be anticipated for a surfactant protein. This suggests that it must undergo a significant conformational change when incorporated into the air-water interface that may involve a hinge-bending, clamshell opening of the separate helix and sheet segments to expose hydrophobic faces to air while maintaining the highly polar surfaces in contact with the underlying water layer. This model is supported by direct observation of the relative orientations of secondary structure elements at the interface by infrared reflection absorption spectroscopy, and by protein packing densities determined from neutron reflectivity profiles.

  • Organizational Affiliation

    WestChem Department of Chemistry, University of Glasgow, Glasgow G12 8QQ, Scotland, United Kingdom.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
RANASPUMIN-298Engystomops pustulosusMutation(s): 0 
Find proteins for B5DCK2 (Engystomops pustulosus)
Explore B5DCK2 
Go to UniProtKB:  B5DCK2
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupB5DCK2
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Method: SOLUTION NMR
  • Conformers Calculated: 100 
  • Conformers Submitted: 25 
  • Selection Criteria: LEAST RESTRAINT VIOLATION 

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2009-06-23
    Type: Initial release
  • Version 1.1: 2011-05-08
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Version format compliance