Human beta two microglobulin: Difference between revisions
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=Human Beta two microglobulin | =Human Beta two microglobulin= | ||
==Beta two microglubulin in human class I major histocompatibility complex (MHCb2m)== | ==Beta two microglubulin in human class I major histocompatibility complex (MHCb2m)== | ||
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[[Image:Human b2m bound to MHC-1 .jpg.jpg]] [[Image:Momeric human b2m.png]] | [[Image:Human b2m bound to MHC-1 .jpg.jpg]] [[Image:Momeric human b2m.png]] | ||
Fig.1. crystal structures of MHCb2m and Mhb2m | Fig.1. crystal structures of MHCb2m (left)and Mhb2m (right) | ||
Both of the two strucures adopt seven-stranded β sandwich fold. The most significant difference in the ctrystal structures | Both of the two strucures adopt seven-stranded β sandwich fold. The most significant difference in the ctrystal structures | ||
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50-56 of MHCb2m form two short β strands that separated by a two residue β bulge. These strands (depicted as D1 and D2 in Fig.1) | 50-56 of MHCb2m form two short β strands that separated by a two residue β bulge. These strands (depicted as D1 and D2 in Fig.1) | ||
each forms three main-chain-main-chain hydrogen bonds to the adjacent β strand E. The bulge in MHCb2m effectively twists the | each forms three main-chain-main-chain hydrogen bonds to the adjacent β strand E. The bulge in MHCb2m effectively twists the | ||
edge strand, which facilitate its binding to the surface of the heavy chain. However, β bulge no longer exits in the crytal | edge strand, which facilitate its binding to the surface of the heavy chain. However, this β bulge no longer exits in the crytal | ||
strucure of Mhb2m | strucure of Mhb2m. The conformation of D strand in Mhb2m provides an ideal assembly surface, making this edge-strand pair vulnerable to aggregation. The hydrogen-bonding potential of strand D is satisfied by the formation intermolecular interactionswith adjecent molecules, demonstrating the potential for this region to propagate assembly through edge-strand interactions. | ||
In addition, the changes observed in strand D result in differenr orientations of the side chains of residues 50-54. As a result, | |||
His-51 (which points inwards in the structure of MHCb2m) rotates by approximately 180, such that it now points away from the hydrophobic core of the protein. This would remove the second protevtive feature from the edge strand, facilitating further interaction in this region. | |||
[[Image:His51.jpg]] | |||
Fig.2. Ribbon diagram showing the position of HIs-51 in the crystal structure of Mhb2m (left) and MHCb2m (right) | |||
