Crystal Structure of the Possum Milk Whey Lipocalin Trichosurin at pH 4.6 with Bound 4-ethylphenol

Experimental Data Snapshot

  • Resolution: 1.50 Å
  • R-Value Free: 0.241 
  • R-Value Work: 0.226 

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Three-dimensional structure and ligand binding properties of trichosurin, a metatherian lipocalin from the milk whey of the common brushtail possum Trichosurus vulpecula

Watson, R.P.Demmer, J.Baker, E.N.Arcus, V.L.

(2007) Biochem J 408: 29-38

  • DOI: https://doi.org/10.1042/BJ20070567
  • Primary Citation of Related Structures:  
    2R73, 2R74, 2RA6

  • PubMed Abstract: 

    Lipocalins are extracellular proteins (17-25 kDa) that bind and transport small lipophilic molecules. The three-dimensional structure of the first lipocalin from a metatherian has been determined at different values of pH both with and without bound ligands. Trichosurin, a protein from the milk whey of the common brushtail possum, Trichosurus vulpecula, has been recombinantly expressed in Escherichia coli, refolded from inclusion bodies, purified and crystallized at two different pH values. The three-dimensional structure of trichosurin was solved by X-ray crystallography in two different crystal forms to 1.9 A (1 A=0.1 nm) and 2.6 A resolution, from crystals grown at low and high pH values respectively. Trichosurin has the typical lipocalin fold, an eight-stranded anti-parallel beta-barrel but dimerizes in an orientation that has not been seen previously. The putative binding pocket in the centre of the beta-barrel is well-defined in both high and low pH structures and is occupied by water molecules along with isopropanol molecules from the crystallization medium. Trichosurin was also co-crystallized with a number of small molecule ligands and structures were determined with 2-naphthol and 4-ethylphenol bound in the centre of the beta-barrel. The binding of phenolic compounds by trichosurin provides clues to the function of this important marsupial milk protein, which is highly conserved across metatherians.

  • Organizational Affiliation

    Laboratory of Structural Biology, School of Biological Sciences, University of Auckland, Private Bag 92-019, Auckland, New Zealand.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
A, B, C, D
166Trichosurus vulpeculaMutation(s): 1 
Find proteins for Q29147 (Trichosurus vulpecula)
Explore Q29147 
Go to UniProtKB:  Q29147
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ29147
Sequence Annotations
  • Reference Sequence
Small Molecules
Ligands 4 Unique
IDChains Name / Formula / InChI Key2D Diagram3D Interactions
Query on ETY

Download Ideal Coordinates CCD File 
CA [auth D],
H [auth A],
P [auth B],
V [auth C]
C8 H10 O
Query on ZN

Download Ideal Coordinates CCD File 
E [auth A]
K [auth B]
L [auth B]
S [auth C]
Y [auth D]
E [auth A],
K [auth B],
L [auth B],
S [auth C],
Y [auth D],
Z [auth D]
Query on IPA

Download Ideal Coordinates CCD File 
DA [auth D]
EA [auth D]
I [auth A]
J [auth A]
Q [auth B]
DA [auth D],
EA [auth D],
I [auth A],
J [auth A],
Q [auth B],
R [auth B],
W [auth C],
X [auth C]
C3 H8 O
Query on CL

Download Ideal Coordinates CCD File 
AA [auth D]
BA [auth D]
F [auth A]
G [auth A]
M [auth B]
AA [auth D],
BA [auth D],
F [auth A],
G [auth A],
M [auth B],
N [auth B],
O [auth B],
T [auth C],
U [auth C]
Binding Affinity Annotations 
IDSourceBinding Affinity
ETY PDBBind:  2RA6 Kd: 3.00e+4 (nM) from 1 assay(s)
Experimental Data & Validation

Experimental Data

  • Resolution: 1.50 Å
  • R-Value Free: 0.241 
  • R-Value Work: 0.226 
  • Space Group: P 1 21 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 44.318α = 90
b = 100.47β = 90.02
c = 84.702γ = 90
Software Package:
Software NamePurpose
XSCALEdata scaling

Structure Validation

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Entry History 

Deposition Data

  • Released Date: 2007-11-20 
  • Deposition Author(s): Watson, R.P.

Revision History  (Full details and data files)

  • Version 1.0: 2007-11-20
    Type: Initial release
  • Version 1.1: 2011-07-13
    Changes: Version format compliance
  • Version 1.2: 2021-11-10
    Changes: Database references, Derived calculations
  • Version 1.3: 2023-10-25
    Changes: Data collection, Refinement description