1QIX

Porcine pancreatic elastase complexed with human beta-casomorphin-7

• PDB DOI: https://doi.org/10.2210/pdb1QIX/pdb

• Classification: SERINE PROTEINASE
• Organism(s): Homo sapiens, Sus scrofa
• Mutation(s): No 


• Deposited: 1999-06-18 Released: 1999-12-14 
• Deposition Author(s): Wilmouth, R.C., Clifton, I.J., Hajdu, J., Schofield, C.J.

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Experimental Data Snapshot

• Method: X-RAY DIFFRACTION
• Resolution: 1.90 Å
• R-Value Free: 0.219 
• R-Value Work: 0.172 

Starting Model: experimental

Literature

Structure of a Specific Acyl-Enzyme Complex Formed between Beta-Casomorphin-7 and Porcine Pancreatic Elastase

Wilmouth, R.C., Clifton, I.J., Robinson, C.V., Roach, P.L., Aplin, R.T., Westwood, N.J., Hajdu, J., Schofield, C.J.

(1997) Nat Struct Biol 4: 456

• PubMed: 9187653 
• DOI: https://doi.org/10.1038/nsb0697-456
• Primary Citation of Related Structures:  
  1QIX


• PubMed Abstract: 
  

  Mass spectrometric screening reveals that an unmodified natural heptapeptide--human beta-casomorphin-7, an internal sequence of human beta-casein that possesses opioid-like activity--reacts with porcine pancreatic elastase to form an unusually stable acyl-enzyme complex at low pH. X-ray crystallographic analysis (to 1.9 A resolution) at pH 5 shows continuous electron density linking the C-terminal isoleucine of beta-casomorphin-7 to Ser 195 through an ester bond. The structure reveals a well defined water molecule (Wat 317), equidistant between the carbon of the ester carbonyl and N epsilon 2 of His 57. Deprotonation of Wat 317 will produce a hydroxide ion positioned to attack the ester carbonyl through the favoured Bürgi-Dunitz trajectory.

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Organizational Affiliation: 

Oxford Centre for Molecular Sciences, UK.

Biological Assembly 1  

Global Symmetry: Asymmetric - C1 
Global Stoichiometry: Hetero 2-mer - A1B1 

Biological assembly 1 generated by PQS (software)

Macromolecule Content

• Total Structure Weight: 26.93 kDa 
• Atom Count: 1,955 
• Modelled Residue Count: 244 
• Deposited Residue Count: 247 
• Unique protein chains: 2

Macromolecules

Entity ID: 1
Molecule	Chains	Sequence Length	Organism	Details	Image
BETA-CASOMORPHIN-7	A	7	Homo sapiens	Mutation(s): 0

Entity ID: 2
Molecule	Chains	Sequence Length	Organism	Details	Image
ELASTASE	B	240	Sus scrofa	Mutation(s): 0  EC: 3.4.21.11 (PDB Primary Data), 3.4.21.36 (UniProt)
UniProt
Find proteins for P00772 (Sus scrofa) Explore P00772  Go to UniProtKB:  P00772

Small Molecules

Ligands 2 Unique
ID	Chains	Name / Formula / InChI Key	2D Diagram
SO4	D [auth B]	SULFATE ION O4 S QAOWNCQODCNURD-UHFFFAOYSA-L
CA	C [auth B]	CALCIUM ION Ca BHPQYMZQTOCNFJ-UHFFFAOYSA-N

Experimental Data & Validation

Experimental Data

• Method: X-RAY DIFFRACTION
• Resolution: 1.90 Å
• R-Value Free: 0.219 
• R-Value Work: 0.172 
• Space Group: P 2₁ 2₁ 2₁

Unit Cell:

Length ( Å )	Angle ( ˚ )
a = 51.282	α = 90
b = 58.24	β = 90
c = 75.437	γ = 90

Software Package:

Software Name	Purpose
REFMAC	refinement
MOSFLM	data reduction
SCALA	data scaling

Structure Validation

Entry History 

Deposition Data

• Released Date: 1999-12-14 
Deposition Author(s): Wilmouth, R.C., Clifton, I.J., Hajdu, J., Schofield, C.J.

Revision History  

• Version 1.0: 1999-12-14
  Type: Initial release
  
• Version 1.1: 2011-05-08
  Changes: Version format compliance
• Version 1.2: 2011-07-13
  Changes: Version format compliance
• Version 1.3: 2023-12-13
  Changes: Data collection, Database references, Derived calculations, Refinement description
• Version 1.4: 2024-11-13
  Changes: Structure summary