Xray structure of domain-swapped cystatin E dimer

Experimental Data Snapshot

  • Resolution: 2.90 Å
  • R-Value Free: 0.273 
  • R-Value Work: 0.268 
  • R-Value Observed: 0.268 

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Structural and functional analysis of cystatin E reveals enzymologically relevant dimer and amyloid fibril states.

Dall, E.Hollerweger, J.C.Dahms, S.O.Cui, H.Haussermann, K.Brandstetter, H.

(2018) J Biol Chem 293: 13151-13165

  • DOI: https://doi.org/10.1074/jbc.RA118.002154
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 

    Protein activity is often regulated by altering the oligomerization state. One mechanism of multimerization involves domain swapping, wherein proteins exchange parts of their structures and thereby form long-lived dimers or multimers. Domain swapping has been specifically observed in amyloidogenic proteins, for example the cystatin superfamily of cysteine protease inhibitors. Cystatins are twin-headed inhibitors, simultaneously targeting the lysosomal cathepsins and legumain, with important roles in cancer progression and Alzheimer's disease. Although cystatin E is the most potent legumain inhibitor identified so far, nothing is known about its propensity to oligomerize. In this study, we show that conformational destabilization of cystatin E leads to the formation of a domain-swapped dimer with increased conformational stability. This dimer was active as a legumain inhibitor by forming a trimeric complex. By contrast, the binding sites toward papain-like proteases were buried within the cystatin E dimer. We also showed that the dimers could further convert to amyloid fibrils. Unexpectedly, cystatin E amyloid fibrils contained functional protein, which inhibited both legumain and papain-like enzymes. Fibril formation was further regulated by glycosylation. We speculate that cystatin amyloid fibrils might serve as a binding platform to stabilize the pH-sensitive legumain and cathepsins in the extracellular environment, contributing to their physiological and pathological functions.

  • Organizational Affiliation

    From the Department of Biosciences, University of Salzburg, A-5020 Salzburg, Austria and.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
A, B
131Homo sapiensMutation(s): 0 
Gene Names: CST6
UniProt & NIH Common Fund Data Resources
Find proteins for Q15828 (Homo sapiens)
Explore Q15828 
Go to UniProtKB:  Q15828
GTEx:  ENSG00000175315 
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ15828
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 2.90 Å
  • R-Value Free: 0.273 
  • R-Value Work: 0.268 
  • R-Value Observed: 0.268 
  • Space Group: P 2 2 21
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 31.62α = 90
b = 64.07β = 90
c = 147.73γ = 90
Software Package:
Software NamePurpose
MOSFLMdata reduction
SCALAdata scaling

Structure Validation

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Entry History & Funding Information

Deposition Data

Funding OrganizationLocationGrant Number
Austrian Science FundAustriaW_01213

Revision History  (Full details and data files)

  • Version 1.0: 2018-07-11
    Type: Initial release
  • Version 1.1: 2018-09-05
    Changes: Data collection, Database references
  • Version 1.2: 2024-01-17
    Changes: Data collection, Database references, Refinement description