Human beta two microglobulin: Difference between revisions
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==<scene name='Human_beta_two_microglobulin/Mhb2m/4'>Monomeric human b2m (Mhb2m)</scene> | ==Monomeric human b2m (Mhb2m)== | ||
The first crystal structure of <scene name='Human_beta_two_microglobulin/Mhb2m/4'>Monomeric human b2m (Mhb2m)</scene> is solved in 2002. The protein is 99 residue in length and has a | |||
seven-stranded β sandwich fold typical of the Immunoglobulin superfamily. It is stabilized by a single disulfide bond between | seven-stranded β sandwich fold typical of the Immunoglobulin superfamily. It is stabilized by a single disulfide bond between | ||
Cys-25 and Cys-80, which links the two β sheets. | Cys-25 and Cys-80, which links the two β sheets. | ||
| Line 23: | Line 23: | ||
Fig.1. crystal structures of MHCb2m (left)and Mhb2m (right) | 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 with a short C' β strand located in the loop connecting strands C | ||
of Mhb2m and MHCb2m involves residues in β strand D and the succeeding loop. When complexed with the MHC heavy chain, residues | and D. The most significant difference in the ctrystal structures of Mhb2m and MHCb2m involves residues in β strand D and the succeeding loop. When complexed with the MHC heavy chain, residues 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 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. 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. | ||
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 | |||
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. 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, | In addition, the changes observed in strand D result in differenr orientations of the side chains of residues 50-54. As a result, | ||
| Line 36: | Line 32: | ||
Fig.2. Ribbon diagram showing the position of HIs-51 in the crystal structure of Mhb2m (left) and MHCb2m (right) | Fig.2. Ribbon diagram showing the position of HIs-51 in the crystal structure of Mhb2m (left) and MHCb2m (right) | ||
==Amyloid Fibril formation of Mhb2m in vitro== | |||
