Streptomyces papain inhibitor (SPI)

Experimental Data Snapshot

  • Resolution: 1.50 Å
  • R-Value Free: 0.184 
  • R-Value Work: 0.163 
  • R-Value Observed: 0.164 

Starting Model: experimental
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Illuminating structure and acyl donor sites of a physiological transglutaminase substrate from Streptomyces mobaraensis.

Juettner, N.E.Schmelz, S.Bogen, J.P.Happel, D.Fessner, W.D.Pfeifer, F.Fuchsbauer, H.L.Scrima, A.

(2018) Protein Sci 27: 910-922

  • DOI: https://doi.org/10.1002/pro.3388
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 

    Transglutaminase from Streptomyces mobaraensis (MTG) has become a powerful tool to covalently and highly specifically link functional amines to glutamine donor sites of therapeutic proteins. However, details regarding the mechanism of substrate recognition and interaction of the enzyme with proteinaceous substrates still remain mostly elusive. We have determined the crystal structure of the Streptomyces papain inhibitory protein (SPI p ), a substrate of MTG, to study the influence of various substrate amino acids on positioning glutamine to the active site of MTG. SPI p exhibits a rigid, thermo-resistant double-psi-beta-barrel fold that is stabilized by two cysteine bridges. Incorporation of biotin cadaverine identified Gln-6 as the only amine acceptor site on SPI p accessible for MTG. Substitution of Lys-7 demonstrated that small and hydrophobic residues in close proximity to Gln-6 favor MTG-mediated modification and are likely to facilitate introduction of the substrate into the front vestibule of MTG. Moreover, exchange of various surface residues of SPI p for arginine and glutamate/aspartate outside the glutamine donor region influences the efficiency of modification by MTG. These results suggest the occurrence of charged contact areas between MTG and the acyl donor substrates beyond the front vestibule, and pave the way for protein engineering approaches to improve the properties of artificial MTG-substrates used in biomedical applications.

  • Organizational Affiliation

    The Department of Chemical Engineering and Biotechnology, University of Applied Sciences of Darmstadt, Darmstadt, Germany.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Papain inhibitor
A, B
110Streptomyces mobaraensisMutation(s): 0 
Find proteins for P86242 (Streptomyces mobaraensis)
Explore P86242 
Go to UniProtKB:  P86242
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP86242
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 1.50 Å
  • R-Value Free: 0.184 
  • R-Value Work: 0.163 
  • R-Value Observed: 0.164 
  • Space Group: P 21 21 21
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 37.35α = 90
b = 45.08β = 90
c = 112.84γ = 90
Software Package:
Software NamePurpose
XDSdata reduction
XSCALEdata scaling

Structure Validation

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Entry History & Funding Information

Deposition Data

Funding OrganizationLocationGrant Number
Helmholtz AssociationGermanyVH-NG-727

Revision History  (Full details and data files)

  • Version 1.0: 2018-03-07
    Type: Initial release
  • Version 1.1: 2018-05-02
    Changes: Data collection, Database references
  • Version 1.2: 2024-01-17
    Changes: Data collection, Database references, Refinement description