Sandbox Reserved 350: Difference between revisions

From Proteopedia
Jump to navigationJump to search
No edit summary
No edit summary
 
(153 intermediate revisions by the same user not shown)
Line 1: Line 1:
<!-- PLEASE DO NOT DELETE THIS TEMPLATE -->
<!-- PLEASE DO NOT DELETE THIS TEMPLATE -->
{{Template:Sandbox_Reserved_BCMB307}}
{{Template:Sandbox_Reserved_BCMB307}}
  <!-- PLEASE ADD YOUR CONTENT BELOW HERE -->
  <!-- PLEASE ADD YOUR CONTENT BELOW HERE -->


Protein: cHuman Coagulation factor V, 1czv
:Protein: cHuman Coagulation factor V, 1czv <ref name="Pubmed">PMID: 10586886 </ref>
{{STRUCTURE_1czv|PDB|SCENE=}}
='''Introduction'''=
<br />
Coagulation Factor V originally studied in 1987 by William H. Kane, Akitada Ichinose, Frederick S. Hagen and Earl W. Davie, out of University of Washington, Seattle. <ref name="Old">PMID: 2827731 </ref>
[http://en.wikipedia.org/wiki/Coagulation_cascade Coagulation] is a complex cascade of a biological reaction that takes place after an injury causing bleeding, to prevent bleeding; A step of hemostatsis, which facilitates the formation of fibrin.  There approximately 30 known factors which play a role in this massive cascade response.  A possible explanation for the sheer complexity associated with what is known about this cascade is that tight regulation for the formation of blood clots are crucial.
<br />
The role of Human Coagulation Factor V is to act as a cofactor along with Factor X and Prothrombin (Factor II, inactive) to form a [http://en.wikipedia.org/wiki/Prothrombinase Prothrombinase] complex activating Prothrobin to Thrombin (FIIa).  Thrombin is then able to activate Fibrinogen (Factor I) into Fibrin (FIa), which connects platelets bound at the site of injury; formation of a clot.
<br />
It is vital for controlled blood clot formation based on known human diseases/conditions of irregular clotting which are quiet devastating.  Two clear aspects of blood clotting involve either under clotting or excessive clotting.  The inability to form a clot leads to excessive bleeding from a minor abration known as [http://en.wikipedia.org/wiki/Haemophilia hemophila]. <ref name="Hemo">PMID: 21453683 </ref> [http://en.wikipedia.org/wiki/Thrombosis Thrombosis] is the second case, where excessive clotting or clotting when no wound is present results in free floating embolisms or thombuses. <ref name="Throm">PMID: 21455860 </ref> Floating free in the blood allows the thrombus to lodge itself within the circulatory system, interferring with orgran downstream of the circulating blood.  Unusual blood circulation/clotting by a thrombus are causes of heart attacks, strokes and necrosis of tissue. <ref name="Throm2">PMID: 21359071 </ref>


{{STRUCTURE_1czv|PDB=1czv|SCENE=}}


<Structure load='1czv'size='500' frame='true' align='right' caption='This is what i'm showing you' scene='Insert optional scene name here' />
__TOC__
=Structure & Function=
The structure of Human Coagulation Factor V (FV) precursors from a translated polypeptide
<br /> to a A1-A2-B-A3-C1-C2 layout which results in the activated (FVa) protein.<ref name="Pubmed"/> 
<br />
*'''Heavy A1-A2 Chain'''
 
*'''Light A3-C1-C2 Chain'''
 
The '''C2 Domain''' of FVa (FVa-C2) consists of a conserved '''<font color='red'> β-Barrel  framework </font> ''' acting as a scaffold for <font color='orangered'> '''three loops''' </font> being part of the light chain. <ref name="Pubmed"/>
<br />
[[Image:3D Jellow B-Barrel Motif.png|thumb|left|upright=1.5|alt=Distorted Jelly-Roll β-barrel motif with three active loops. The β-barrel motif is labeled in red and the three loops in orange.|Secondary structure of C2 Domain of 1czv.]]
<br />
'''The FVa-C2''', which is classified as a ''' <font color='red'> distorted jelly-roll </font> ''' <scene name='Sandbox_Reserved_350/Expriment3/1'> β-barrel motif </scene>, is composed of <scene name='Sandbox_Reserved_350/Expriment5/1'> eight major antiparallel strands  </scene> arranged into two ''' <font color='lawngreen'> β-sheets of five </font> and <font color='maroon'> three strands </font> ''' packed against one another.
<br />
Salt bridges located within the "upper" segment ''' <font color='goldenrod'> (Asp61-Arg134) </font>.  The C2-Domain of Human coagulation factor is homologous to a larger family of adhesion proteins; [http://proteopedia.org/wiki/index.php/Category:Discoidin_family Discoidin], but not related to synaptotagmin-like C2 domains.<ref name="Pubmed"/>
<br />
<br />
<br />
<br />
<br />
<br />
<br />
 
<scene name='Sandbox_Reserved_350/Expriment2/4'> '''The Three Loops'''</scene>  <ref name="Pubmed"/>
<br />
*'''Apex 1'''—<font color='purple'>'''Ser21-Trp31;''' containing Indole moieties able to form hydrogen bonds (Involving two consecutive Trp 26 & 27). </font>
 
*'''Apex 2'''—<font color='lightseagreen'>'''Asn39-Asn45;''' capped with a basic residue able to form hydrogen bonds (Arg43). </font>
 
*'''Apex 3'''—<font color='deeppink'>'''Gly75-Tyr84;''' Hydrophobic Loop (Leu79). </font>
<Structure load='1czv' size='' frame='true' align='right' caption=' C2 Domain of Human Coagulation Factor V' scene='Sandbox_Reserved_350/Expriment3/2'/>
 
The apexes of these <font color='orangered'> '''three loops''' </font> within the C2 domain, are able to create a deep groove lined by '''hydrophobic''' <font color='brown'> '''(Trp31, Met83)''' </font> and '''polar residues''' <font color='royalblue'> '''(Gln48, Ser78)'''</font>, as seen and consisting the <scene name='Sandbox_Reserved_350/Expriment3/3'> Open Form </scene> of FVa-C2.  This groove is seen as the primary membrane-binding site of the C2-Domain. <ref name="Pubmed"/>
<br />
A second dimeric crystal form of FVa-C2, packed through the free edges of S6 strands, presenting a different Leu104-Val109
loop, suggests capabilities of adopting a "Closed Form".  In contrast to the "Open Form" of FVa-C2; when looking at the loops 1 and 3 are tilted towards the interior of the groove.  This change is considered due to a twist around '''Gly28''' cause it to be deformed (pseudo).  In general there is a narrowing of the entrance to the shallow inner loop groove, particularly the critical Gln48 carboxamide; Taking place due form the concerted tilting/ "twisting" of the main chain atoms, shifting up to ~7Å and a 12Å displacement of the Trp27 moiety <big>&rarr;</big> shifting closer to the other two loops.  Once shifted closer, the groove seen in the '''Open Form''' is covered by a hydrophobic ridge of Trp27, Trp27 and Leu79, and now in the '''Closed Form''' with a smaller, 370Å hydrophobic surface compared to 520Å. <ref name="Pubmed"/>
<br />
The three loops are described by ''Macedo-Ribeiro et al.'' to protrude like spikes from the bottom of the barrel in monomeric FVa-C2.<ref name="Pubmed"/>  It is also worth noting that spike (1) & spike (3) are separated by β-hairpin structures and spike (2) is described as a wider irregularly loop comparatively.  These three loops extending from the C2 domain, are all linked to each other, and to '''three shorter loops''' by an intricate '''H-bonding network''' which extends to residues at the bottom of the β-barrel.<ref name="Pubmed"/>
<br />
The overall Barrel structure is closed at the top and bottom by straight segments, giving it an overall spherical shape with a flattened upper surface.
<br />
 
Functionality of Human Coagulation Factor V (FV), as most proteins is strongly correlated to the conformation of the overall structure.  As noted above in the structural section, two structural forms of Human Coagulation Factor V C2 Domain were crystallized.  These two structures were distinct from each other based on a conformational change present, alternating between what was described as a Open and Closed form.  This change from close to open by exposing this groove results due to the kind of environment Human Coagulation Factor V finds itself in, and ultimately the source of its function.  This confers that FV is not an enzymatically active protein, but instead acts a cofactor part of the larger [http://en.wikipedia.org/wiki/File:Coagulation_full.svg Coagulation Cascade.]
<br />
The role of Human Coagulation Factor V, is act as a cofactor, enhances the ability of factor Xa to generate  from prothrombin once activated (Fva).  It is known that FV is activated in a positive feedback mechanism by α-thrombin and aided in conjunction with Human Coagulation Factor Xa, and inhibited by [http://en.wikipedia.org/wiki/Protein_C Active Protein C] [http://www.proteopedia.org/wiki/index.php/1aut (1aut)].
Originally, the activation of FV to Fva was understood to require the excision of B segment between the heavy and light chain at Arg-1018 and Arg-1545.  The peptide as a whole remains united via the disulfide linkage connecting the N and C Terminus and interactions with calcium ions. <ref name="Old"/>  In 1999, the [[#Finer Crystallography Details| crystallization]] of FV in both Fv and Fva was identified providing further insight into the quaternary structure of FV and the underlining mechanism by which the protein functions. <ref name="Pubmed"/>  This mechanism proposed has three novel points, which were over-looked based on assumed knowledge from previous studies modeling the mechanism for FV after the well characterized mechanism of vitamin K-dependent [http://en.wikipedia.org/wiki/Coagulation Coagulation Factors]; [http://en.wikipedia.org/wiki/Factor_VII VII] [http://proteopedia.org/wiki/index.php/1dan (1dan)]
, [http://en.wikipedia.org/wiki/Factor_IX IX] [http://proteopedia.org/wiki/index.php/1pfx (1pfx)]
, [http://en.wikipedia.org/wiki/Factor_X X] [http://proteopedia.org/wiki/index.php/1c5m (1c5m)]
and Protein C <ref name="KA">PMID: 10200912</ref>
<ref name="KB">PMID: 9805008 </ref>
<br />
<br />
The '''Mechanism Proposed''' <ref name="Pubmed"/> differs from the previous work, showing Ca<sup>2+</sup>-Independent stereospecific binding to phospholipid membranes, based on;
<br />
'''(1)'''  Immersion of Hydrophobic residues at the apices of loops in apolar membrane core.
<br />
'''(2)'''  Specific Interactions with phosphatidylserine head groups in the groove enclosed by these loops.
<br />
'''(3)'''  Favourable electrostatic contacts of basic side chains with negatively charged membrane phosphate groups.
<br />
<br />
<br />
 
==Detailed Proposed Mechanism <ref name="Pubmed"/> ==
For stereospecific and cooperative association with (P<sub>ʟ</sub>S)-rich membranes.
<br />
'''(1)'''  FVa, with C2 domain in its closed form, approaches acidic membranes directed by protein-membrane electrostatic interactions.
<br />
'''(2)'''  One or two (P<sub>ʟ</sub>S) molecules bind to anchoring points Arg150 or Gln48 in small groove of closed from → triggers widening of the groove and conversion to the open form.
<br />
'''(3)''' [(Fig. 5a.)]–A (P<sub>ʟ</sub>S) molecule occupies the opened specificity pocket.
<br />
'''(4)''' Now the unfolded hydrophobic spikes, perforate the polar membrane surface; Trp26, Trp27 and Leu79 side are immersed into the apolar core.
<br />
'''(5)''' Bottom of β-Barrel contacts negatively charged phosphate head groups on the membrane through favourable ionic interactions with basic residues located in the spikes and neighboring loops. <ref name="Lipid-protein blood interaction ">PMID: 9805008 </ref> <ref name="Prothrobins and lipids ">PMID: 2261453 </ref>
<br />
<br />
:The C2 domain of FVa is essential for binding to phosphatidyl-ʟ-serine (P<sub>ʟ</sub>S).  This is because the spikes and neighboring loops are highly connected and several continuous P<sub>ʟ</sub>S molecules would be necessary for association with spike unfolding and membrane insertion for a cooperative mechanism.  This assures FVa-C2 binds only to cell membranes with the concentration of P<sub>ʟ</sub>S exceeding a critical threshold level and therefore selectively target FVa to procoagulated, P<sub>ʟ</sub>S-rich surfaces.
<br />
 
<br />
===Experimental Evidence  ===
Binding of FVa to a few acidic, lipid-specific sites results in substantial protein conformational changes. <ref name="Pubmed"/>
<br />
*A3 Domain interacts with phosphatidyl-choline. <ref name="FVa and Light chain cofactor ">PMID: 8286378 </ref>
*Contributions from hydrophobicity of the heavy chains; A1 and A2. <ref name="Role of Heavy Chains in FVa ">PMID: 9370458 </ref>
*Speculation of further conformational changes as associated with membrane, where the C2 Domain rotates to bring spike 1 and the Trp-rich surface (flat and extended) covering the front-side of the β-Barrel in contact with the phospholipid membrane [(Fig. 5b.)]. <ref name="Pubmed"/>
<br />
<br />
<br />
<br />
 
=Finer Crystallography Details=
''[http://www.rcsb.org/pdb/explore/materialsAndMethods.do?structureId=1CZV X-Ray Diffraction of the C2 Domain of Human Coagulation Factor V] (1czv)'' <ref name="Pubmed"/>
<br />
'''Resolution Method:'''Structure Replacement
<br />
'''Resolution:''' 2.40Å
<br />
: ''High:'' 2.40Å
: ''Low:''  8.00Å
<br />
'''Condition;'''
<br />
::''pH:'' 10.00
 
::''Temperature:'' 289.0K
 
::''Number of Crystals used:'' 1
<br />
'''Geometry:''' ''Unit Cell Length''        :          ''Angle''
<br />
:::a= 86.52Å                    :            α= 90°
 
:::b= 70.54Å                    :            β= 90°
 
:::c= 60.58Å                    :            γ= 90°
<br />
'''Radiation Source:''' Rotating Anode
<br />
'''Wavelength OR Range:''' 1.5418Å
<br />
'''Detector Type:''' Image Plate
 
=References=
 
<references/>