3QTL

Structural Basis for Dual-inhibition Mechanism of a Non-classical Kazal-type Serine Protease Inhibitor from Horseshoe Crab in Complex with Subtilisin


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.6 Å
  • R-Value Free: 0.269 
  • R-Value Work: 0.199 

wwPDB Validation 3D Report Full Report


This is version 1.2 of the entry. See complete history

Literature

Structural basis for dual-inhibition mechanism of a non-classical kazal-type serine protease inhibitor from horseshoe crab in complex with subtilisin.

Shenoy, R.T.Thangamani, S.Velazquez-Campoy, A.Ho, B.Ding, J.L.Sivaraman, J.

(2011) Plos One 6: e18838-e18838

  • DOI: 10.1371/journal.pone.0018838

  • PubMed Abstract: 
  • Serine proteases play a crucial role in host-pathogen interactions. In the innate immune system of invertebrates, multi-domain protease inhibitors are important for the regulation of host-pathogen interactions and antimicrobial activities. Serine pro ...

    Serine proteases play a crucial role in host-pathogen interactions. In the innate immune system of invertebrates, multi-domain protease inhibitors are important for the regulation of host-pathogen interactions and antimicrobial activities. Serine protease inhibitors, 9.3-kDa CrSPI isoforms 1 and 2, have been identified from the hepatopancreas of the horseshoe crab, Carcinoscorpius rotundicauda. The CrSPIs were biochemically active, especially CrSPI-1, which potently inhibited subtilisin (Ki = 1.43 nM). CrSPI has been grouped with the non-classical Kazal-type inhibitors due to its unusual cysteine distribution. Here we report the crystal structure of CrSPI-1 in complex with subtilisin at 2.6 Å resolution and the results of biophysical interaction studies. The CrSPI-1 molecule has two domains arranged in an extended conformation. These two domains act as heads that independently interact with two separate subtilisin molecules, resulting in the inhibition of subtilisin activity at a ratio of 1:2 (inhibitor to protease). Each subtilisin molecule interacts with the reactive site loop from each domain of CrSPI-1 through a standard canonical binding mode and forms a single ternary complex. In addition, we propose the substrate preferences of each domain of CrSPI-1. Domain 2 is specific towards the bacterial protease subtilisin, while domain 1 is likely to interact with the host protease, Furin. Elucidation of the structure of the CrSPI-1: subtilisin (1∶2) ternary complex increases our understanding of host-pathogen interactions in the innate immune system at the molecular level and provides new strategies for immunomodulation.


    Organizational Affiliation

    Department of Biological Sciences, National University of Singapore, Singapore, Singapore.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
Subtilisin-like serin protease
A, B, C
274Bacillus licheniformisMutation(s): 0 
Gene Names: apr
Find proteins for Q6PNN5 (Bacillus licheniformis)
Go to UniProtKB:  Q6PNN5
Entity ID: 2
MoleculeChainsSequence LengthOrganismDetails
Kazal-type serine protease inhibitor SPI-1
D
75Carcinoscorpius rotundicaudaMutation(s): 0 
Gene Names: SPI-1
Find proteins for A1X1V8 (Carcinoscorpius rotundicauda)
Go to UniProtKB:  A1X1V8
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.6 Å
  • R-Value Free: 0.269 
  • R-Value Work: 0.199 
  • Space Group: P 1 21 1
Unit Cell:
Length (Å)Angle (°)
a = 73.840α = 90.00
b = 65.072β = 95.44
c = 111.909γ = 90.00
Software Package:
Software NamePurpose
CBASSdata collection
DENZOdata reduction
PHENIXrefinement
REFMACrefinement
SCALEPACKdata scaling
MOLREPphasing
PDB_EXTRACTdata extraction

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2011-06-01
    Type: Initial release
  • Version 1.1: 2011-07-13
    Type: Version format compliance
  • Version 1.2: 2017-11-08
    Type: Refinement description