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PDBsum entry 1fns
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Immune system
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PDB id
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1fns
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Contents |
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214 a.a.
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220 a.a.
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196 a.a.
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* Residue conservation analysis
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References listed in PDB file
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Key reference
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Title
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Von willebrand factor conformation and adhesive function is modulated by an internalized water molecule.
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Authors
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R.Celikel,
Z.M.Ruggeri,
K.I.Varughese.
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Ref.
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Nat Struct Biol, 2000,
7,
881-884.
[DOI no: ]
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PubMed id
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Abstract
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Platelet participation in hemostasis and arterial thrombosis requires the
binding of glycoprotein (GP) Ibalpha to von Willebrand factor (vWF). Hemodynamic
forces enhance this interaction, an effect mimicked by the substitution I546V in
the vWF A1 domain. A water molecule becomes internalized near the deleted Ile
methyl group. The change in hydrophobicity of the local environment causes
positional changes propagated over a distance of 27 A. As a consequence, a major
reorientation of a peptide plane occurs in a surface loop involved in GP Ibalpha
binding. This distinct vWF conformation shows increased platelet adhesion and
provides a structural model for the initial regulation of thrombus formation.
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Figure 1.
Figure 1. Location of the I546V mutation and its effects on
platelet adhesion. a, Stereo view of the vWF A1 domain
presented as a ribbon structure, with  -strands
in yellow and  -helices
in purple connected by loops. Note the position of the side
chain of Ile 546. The loops preceding and following strand 3,
site of the major conformational changes caused by the I546V
substitution, are colored in green. The figure was produced with
Bobscript^28. b, Velocity of platelets rolling on wild-type or
I546V mutant vWF A1 domain in a flow field with wall shear rate
of 1500 s^ -1. Results are presented as number of platelets
within defined velocity categories. Platelets rolling on the
mutant A1 domain had a median velocity of 4.2  m
s^-1 compared to 44.7 m
s^ -1 on the wild type control. A video clip showing the real
time interaction of flowing platelets with wild type and mutant
A1 domain is provided as supplementary material.
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Figure 4.
Figure 4. Platelet adhesion to mutant vWF A1 domain fragments.
Amino acid substitutions are indicated with the one letter code
of the native and mutant residues. Single substitutions with Ala
caused essentially complete loss of function at the following
positions: Glu 557 in strand 2;
His 559 in loop 2-
3;
Tyr 565 in strand 3;
Lys 572 in loop 3-
2;
Glu 596 and Lys 599 in helix 3.
The G561S substitution in the 2-
3
loop impaired the function of the wild type A1 domain as well as
of the I546V mutant. In contrast, control mutations of Lys 585
in loop 2-
3,
Arg 632 in helix 4,
Lys 644 in loop 4-
5,
and His 656 in loop 5-
5
had minimal or no effect on function. The number of surface
interacting platelets was counted between 1 and 4 min from the
beginning of flow; the wall shear rate was 1,500 s^-1. The
results of mutant fragments are expressed as a percentage of
those obtained with a wild type control tested on the same
experimental day. The average number of platelets interacting
with wild type vWF fragment was 57 (n = 11). The results
represent the mean with standard error of the mean of two to
four separate experiments performed with each mutant fragment.
Video clips can be viewed on the following web
sites:http://www.scripps.edu/mem/biochem/KI and
http://www.scripps.edu/mem/eht/ruggeri. These clips show the
rolling of platelets, seen as white round objects, tethered to
immobilized wild type A1 domain (top half of the screen) or
I546V mutant A1 domain (lower half of the screen). The wall
shear rate was 1500 s^ -1. Platelets interacting with the mutant
A1 domain roll with considerably lower velocity (median = 4.2
m
s^-1) than those interacting with the wild type control (median
= 44.7 m
s^ -1). The few larger objects that appear transiently in both
screens and move rapidly are leukocytes that interact briefly
with activated platelets on the surface.
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The above figures are
reprinted
by permission from Macmillan Publishers Ltd:
Nat Struct Biol
(2000,
7,
881-884)
copyright 2000.
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Secondary reference #1
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Title
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Crystal structure of the von willebrand factor a1 domain in complex with the function blocking nmc-4 FAB.
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Authors
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R.Celikel,
K.I.Varughese,
Madhusudan,
A.Yoshioka,
J.Ware,
Z.M.Ruggeri.
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Ref.
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Nat Struct Biol, 1998,
5,
189-194.
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PubMed id
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