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! <applet load='1r70' size='200' frame='true' align='left' />
! <applet load='1r70' size='200' frame='true' align='left' />
|IgM: Solution structure of human Immunoglobulin M [[2rcj]]
|<scene name='Rebecca_Martin/Sandbox1/Igg_y_shape/1'>IgG</scene>


IgG: Crystal structure of the intact human IgG B12 with broad and potent activity against primary HIV-1 isolates: a template for HIV vaccine design [[1hzh]]
<scene name='Rebecca_Martin/Sandbox1/Igg_disulfides/1'>IgG: disulfide bonds connecting the heavy and light chains</scene>


IgG: Three=dimensional structure of a human immunoglobulin with a hinge deletion [[1mco]]
<scene name='Rebecca_Martin/Sandbox1/Igg_glycines/1'>IgG: glycines (black) make the hinge region more flexible</scene>


IgD: Semi-extended solution structure of human myeloma immunoglobulin D determined by constrained X-ray scattering [[1zvo]]
<scene name='Rebecca_Martin/Sandbox1/Igg_mutant/1'>IgG with hinge deletion</scene> (missing one fab fragment. Note the T-shape.


IgE: Structure of the human ige-fc bound to its high affinity receptor fc(epsilon)ri(alpha) [[1f6a]]
<scene name='Rebecca_Martin/Sandbox1/Igg_mutant_no_disulfie/1'>Lack of a disulfide bond between heavy and light chains in above IgG
</scene>
 
<scene name='Rebecca_Martin/Sandbox1/Igm_pentamer/1'>IgM pentamer</scene>
 
<scene name='Rebecca_Martin/Sandbox1/Igm/1'>IgM</scene>
 
<scene name='Rebecca_Martin/Sandbox1/Igd/1'>IgD</scene> Hinge region is 64 amino acids in length. Note similarity to IgA.
|}
|}


== The J Chain allows IgA to form Dimers==
== The J Chain allows IgA to form Dimers==
<applet load='2qtj' size='400' frame='true' align='right' caption='dimeric IgA1' />  
<applet load='2qtj' size='425' frame='true' align='right' caption='dimeric IgA1' />  
:The IgA structure has an addition 18 kDa, 137 residue polypeptide chain called the <scene name='Rebecca_Martin/Sandbox1/Iga1_dimeric/2'>J chain</scene> <ref name ="ten" />. This 18 kDa, 137-residue polypeptide chain is comprised of 2 immunoglobulin-like domains. The J chain is covalently attached to the C terminal Cys471 on IgA's Ch3 domain <ref name="eight">PMID: 18178841</ref> via a disulfide bridge with either the J chain’s Cys 14 or the Cys 68 <ref name="ten"/>, <ref name="eight"/>. The J chain has a single N-linked oligosaccharide 15111057, which increases rigidity and offers protection against proteases. The J chain allows IgA to form <scene name='Rebecca_Martin/Sandbox1/Iga1_dimeric/1'>dimers</scene> dimers, and less often trimer and tetramers. These polymers are rare because steric hindrance from the T-shaped Fab regions makes polymerization thermodynamically unfavorable.  
:The IgA structure has an addition 18 kDa, 137 residue polypeptide chain called the <scene name='Rebecca_Martin/Sandbox1/Iga1_dimeric/2'>J chain</scene> <ref name ="ten" />. This 18 kDa, 137-residue polypeptide chain is comprised of 2 immunoglobulin-like domains. The J chain is covalently attached to the C terminal Cys471 on IgA's Ch3 domain <ref name="eight">PMID: 18178841</ref> via a disulfide bridge with either the J chain’s Cys 14 or the Cys 68 <ref name="ten"/>, <ref name="eight"/>. The J chain has a single N-linked oligosaccharide 15111057, which increases rigidity and offers protection against proteases. The J chain allows IgA to form <scene name='Rebecca_Martin/Sandbox1/Iga1_dimeric/1'>dimers</scene> dimers, and less often trimer and tetramers. These polymers are rare because steric hindrance from the T-shaped Fab regions makes polymerization thermodynamically unfavorable.  


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==sIgA1 and sIgA2==  
==sIgA1 and sIgA2==  
[[Image:SIgA.jpg|thumb|Adapted from Bonner, et al 2009 and Bonner, et al 2008.]]
[[Image:SIgA.jpg|thumb|Adapted from Bonner, et al 2009 and Bonner, et al 2008.]]
:Binding of the secretory component to the convex edge of the Fc region of IgA1 maintains dimeric IgA1 in a near planar conformation, <ref name="nineten" />, <ref name="eight" />. The Fc regions align end to end without overlap, and the fab fragments remain in alignment with the Fc plane. In contrast, sIgA2 fab fragments remain out of alignment with the Fc plane. Because the secretory component resides at the convex region of the Fc portion, the D1 and D5 impart steric hindrance on the fab fragments, which are forced out of alignment. Consequently, IgA2 assumes a nonplanar conformation. The longer hinge region of IgA1 allows it to maintain its planar conformation.  
:Binding of the secretory component to the convex edge of the Fc region of dimeric IgA1 maintains <scene name='Rebecca_Martin/Sandbox1/Siga1def/1'>Secretory IgA1</scene> in a near planar conformation, <ref name="nineten" />, <ref name="eight" />. The Fc regions align end to end without overlap, and the fab fragments remain in alignment with the Fc plane. In contrast, <scene name='Rebecca_Martin/Sandbox1/Siga1/1'>Secretory IgA2</scene> fab fragments remain out of alignment with the Fc plane. Because the secretory component resides at the convex region of the Fc portion, the D1 and D5 impart steric hindrance on the fab fragments, which are forced out of alignment. Consequently, IgA2 assumes a nonplanar conformation. The longer hinge region of IgA1 allows it to maintain its planar conformation.  




Proteopedia Page Contributors and Editors (what is this?)Proteopedia Page Contributors and Editors (what is this?)

Rebecca Martin, Jaime Prilusky
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