2FTL

Crystal structure of trypsin complexed with BPTI at 100K


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.62 Å
  • R-Value Free: 0.227 
  • R-Value Work: 0.214 

wwPDB Validation 3D Report Full Report


This is version 1.3 of the entry. See complete history

Literature

Rigidification of a Flexible Protease Inhibitor Variant upon Binding to Trypsin.

Hanson, W.M.Domek, G.J.Horvath, M.P.Goldenberg, D.P.

(2007) J.Mol.Biol. 366: 230-243

  • DOI: 10.1016/j.jmb.2006.11.003
  • Primary Citation of Related Structures:  2FTM

  • PubMed Abstract: 
  • The Tyr35-->Gly replacement in bovine pancreatic trypsin inhibitor (BPTI) has previously been shown to dramatically enhance the flexibility of the trypsin-binding region of the free inhibitor and to destabilize the interaction with the protease by ab ...

    The Tyr35-->Gly replacement in bovine pancreatic trypsin inhibitor (BPTI) has previously been shown to dramatically enhance the flexibility of the trypsin-binding region of the free inhibitor and to destabilize the interaction with the protease by about 3 kcal/mol. The effects of this replacement on the enzyme-inhibitor interaction were further studied here by X-ray crystallography and isothermal titration calorimetry (ITC). The co-crystal structure of Y35G BPTI bound to trypsin was determined using 1.65 A resolution X-ray diffraction data collected from cryopreserved crystals, and a new structure of the complex with wild-type BPTI under the same conditions was determined using 1.62 A data. These structures reveal that, in contrast to the free protein, Y35G BPTI adopts a conformation nearly identical with that of the wild-type protein, with a water-filled cavity in place of the missing Tyr side-chain. The crystallographic temperature factors for the two complexes indicate that the mutant inhibitor is nearly as rigid as the wild-type protein when bound to trypsin. Calorimetric measurements show that the change in enthalpy upon dissociation of the complex is 2.5 kcal/mol less favorable for the complex containing Y35G BPTI than for the complex with the wild-type inhibitor. Thus, the destabilization of the complex resulting from the Y35G replacement is due to a more favorable change in entropy upon dissociation. The heat capacity changes for dissociation of the mutant and wild-type complexes were very similar, suggesting that the entropic effects probably do not arise from solvation effects, but are more likely due to an increase in protein conformational entropy upon dissociation of the mutant inhibitor. These results define the biophysical role of a highly conserved core residue located outside of a protein-binding interface, demonstrating that Tyr35 has little impact on the trypsin-bound BPTI structure and acts primarily to define the structure of the free protein so as to maximize binding affinity.


    Organizational Affiliation

    Department of Biology, University of Utah, 257 South 1400 East, Salt Lake City, UT 84112-0840, USA.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
Cationic trypsin
E
223Bos taurusEC: 3.4.21.4
Find proteins for P00760 (Bos taurus)
Go to UniProtKB:  P00760
Entity ID: 2
MoleculeChainsSequence LengthOrganismDetails
Pancreatic trypsin inhibitor
I
58Bos taurusN/A
Find proteins for P00974 (Bos taurus)
Go to UniProtKB:  P00974
Small Molecules
Ligands 4 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
NA
Query on NA

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E
SODIUM ION
Na
FKNQFGJONOIPTF-UHFFFAOYSA-N
 Ligand Interaction
SO4
Query on SO4

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E, I
SULFATE ION
O4 S
QAOWNCQODCNURD-UHFFFAOYSA-L
 Ligand Interaction
CA
Query on CA

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E, I
CALCIUM ION
Ca
BHPQYMZQTOCNFJ-UHFFFAOYSA-N
 Ligand Interaction
EDO
Query on EDO

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E
1,2-ETHANEDIOL
ETHYLENE GLYCOL
C2 H6 O2
LYCAIKOWRPUZTN-UHFFFAOYSA-N
 Ligand Interaction
Modified Residues  1 Unique
IDChainsTypeFormula2D DiagramParent
IAS
Query on IAS
E
L-beta-peptide, C-gamma linkingC4 H7 N O4

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Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.62 Å
  • R-Value Free: 0.227 
  • R-Value Work: 0.214 
  • Space Group: I 2 2 2
Unit Cell:
Length (Å)Angle (°)
a = 74.726α = 90.00
b = 81.906β = 90.00
c = 124.261γ = 90.00
Software Package:
Software NamePurpose
HKL-2000data reduction
SCALEPACKdata scaling
CNSrefinement
CNSphasing
HKL-2000data collection

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2006-02-14
    Type: Initial release
  • Version 1.1: 2008-05-01
    Type: Version format compliance
  • Version 1.2: 2011-07-13
    Type: Version format compliance
  • Version 1.3: 2011-07-27
    Type: Database references, Derived calculations, Non-polymer description