Biological Assembly 1  

 3D View: Structure | Electron Density | Ligand Interaction

Global Symmetry: Asymmetric - C1 
Global Stoichiometry: Hetero 3-mer - A1B1C1 

Biological assembly 1 assigned by authors and generated by PISA (software)

Macromolecule Content

• Total Structure Weight: 81.65 kDa 
• Atom Count: 6092 
• Modelled Residue Count: 653 
• Deposited Residue Count: 703 
• Unique protein chains: 3

3B9F

1.6 A structure of the PCI-thrombin-heparin complex

• DOI: 10.2210/pdb3B9F/pdb

• Classification: HYDROLASE/HYDROLASE INHIBITOR
• Organism(s): Homo sapiens
• Expression System: Escherichia coli
• Mutation(s): Yes 


• Deposited: 2007-11-05 Released: 2008-04-22 
• Deposition Author(s): Li, W., Adams, T.E., Huntington, J.A.

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Experimental Data Snapshot

• Method: X-RAY DIFFRACTION
• Resolution: 1.60 Å
• R-Value Free: 0.234 
• R-Value Work: 0.208 
• R-Value Observed: 0.208 

Literature

Molecular basis of thrombin recognition by protein C inhibitor revealed by the 1.6-A structure of the heparin-bridged complex.

Li, W., Adams, T.E., Nangalia, J., Esmon, C.T., Huntington, J.A.

(2008) Proc Natl Acad Sci U S A 105: 4661-4666

• PubMed: 18362344 
• DOI: 10.1073/pnas.0711055105
• Primary Citation of Related Structures:  
  3B9F


• PubMed Abstract: 
  

Protein C inhibitor (PCI) is a serpin with many roles in biology, including a dual role as pro- and anticoagulant in blood. The protease specificity and local function of PCI depend on its interaction with cofactors such as heparin-like glycosaminoglycans (GAGs) and thrombomodulin (TM). Both cofactors significantly increase the rate of thrombin inhibition, but GAGs serve to promote the anticoagulant activity of PCI, and TM promotes its procoagulant function. To gain insight into how PCI recognition of thrombin is aided by these cofactors, we determined a crystallographic structure of the Michaelis complex of PCI, thrombin, and heparin to 1.6 A resolution. Thrombin interacts with PCI in an unusual fashion that depends on the length of PCI's reactive center loop (RCL) to align the heparin-binding sites of the two proteins. The principal exosite contact is engendered by movement of thrombin's 60-loop in response to the unique P2 Phe of PCI. This mechanism of communication between the active site of thrombin and its recognition exosite is previously uncharacterized and may relate to other thrombin substrate-cofactor interactions. The cofactor activity of heparin thus depends on the formation of a heparin-bridged Michaelis complex and substrate-induced exosite contacts. We also investigated the cofactor effect of TM, establishing that TM bridges PCI to thrombin through additional direct interactions. A model of the PCI-thrombin-TM complex was built and evaluated by mutagenesis and suggests distinct binding sites for heparin and TM on PCI. These data significantly improve our understanding of the cofactor-dependent roles of PCI in hemostasis.

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Organizational Affiliation: 

Department of Haematology, Division of Structural Medicine, Thrombosis Research Unit, Cambridge Institute for Medical Research, University of Cambridge, Wellcome Trust/MRC Building, Hills Road, Cambridge CB2 0XY, United Kingdom.

Macromolecules

Entity ID: 1
Molecule	Chains	Sequence Length	Organism	Details	Image
Prothrombin	A [auth L]	49	Homo sapiens	Mutation(s): 0  Gene Names: F2 EC: 3.4.21.5
Find proteins for P00734 (Homo sapiens) Explore P00734  Go to UniProtKB:  P00734
NIH Common Fund Data Resources
PHAROS:  P00734 GTEx:  ENSG00000180210

Entity ID: 2
Molecule	Chains	Sequence Length	Organism	Details	Image
Prothrombin	B [auth H]	259	Homo sapiens	Mutation(s): 1  Gene Names: F2 EC: 3.4.21.5
Find proteins for P00734 (Homo sapiens) Explore P00734  Go to UniProtKB:  P00734
NIH Common Fund Data Resources
PHAROS:  P00734 GTEx:  ENSG00000180210

Entity ID: 3
Molecule	Chains	Sequence Length	Organism	Details	Image
Plasma serine protease inhibitor	C [auth I]	395	Homo sapiens	Mutation(s): 0  Gene Names: SERPINA5, PCI, PLANH3, PROCI
Find proteins for Q9N2I2 (Bos taurus) Explore Q9N2I2  Go to UniProtKB:  Q9N2I2

Oligosaccharides

Help

Entity ID: 4
Molecule	Chains	Chain Length	2D Diagram	Glycosylation
alpha-L-fucopyranose-(1-6)-2-acetamido-2-deoxy-beta-D-glucopyranose	D [auth A]	2		N-Glycosylation

Entity ID: 5
Molecule	Chains	Chain Length	2D Diagram	Glycosylation
2-O-sulfo-alpha-L-idopyranuronic acid-(1-4)-2-deoxy-6-O-sulfo-2-(sulfoamino)-alpha-D-glucopyranose	E [auth B]	2		N/A

Small Molecules

Ligands 2 Unique
ID	Chains	Name / Formula / InChI Key	2D Diagram
SO4	F [auth H], J [auth I], K [auth I]	SULFATE ION O4 S QAOWNCQODCNURD-UHFFFAOYSA-L
GOL	G [auth H], H, I [auth H], L [auth I], M [auth I]	GLYCEROL C3 H8 O3 PEDCQBHIVMGVHV-UHFFFAOYSA-N

Experimental Data & Validation

Experimental Data

• Method: X-RAY DIFFRACTION
• Resolution: 1.60 Å
• R-Value Free: 0.234 
• R-Value Work: 0.208 
• R-Value Observed: 0.208 
• Space Group: P 1

Unit Cell:

Length ( Å )	Angle ( ˚ )
a = 44.055	α = 78.72
b = 48.825	β = 81.52
c = 97.85	γ = 77.69

Software Package:

Software Name	Purpose
CNS	refinement
ADSC	data collection
MOSFLM	data reduction
SCALA	data scaling
PHASER	phasing

Structure Validation

Entry History 

Deposition Data

• Deposited Date: 2007-11-05 
• Released Date: 2008-04-22 
Deposition Author(s): Li, W., Adams, T.E., Huntington, J.A.

Revision History  

• Version 1.0: 2008-04-22
  Type: Initial release
  
• Version 1.1: 2011-07-13
  Changes: Non-polymer description, Version format compliance
• Version 1.2: 2018-04-11
  Changes: Advisory, Data collection, Database references, Source and taxonomy, Structure summary
• Version 2.0: 2020-07-29
  Type: Remediation
  Reason: Carbohydrate remediation
  Changes: Advisory, Atomic model, Data collection, Derived calculations, Structure summary