Sandbox Reserved 1493: Difference between revisions
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The '''αIIb subunit''' (glycoprotein IIb) is composed of 1008 amino acids unevenly distributed over 2 chains. A part forms a light chain which comports a cytoplasmic tail of 20 amino acids and a transmembrane helix. An extracellular disulfide segment links this chain to the <scene name='80/802667/Alpha_head/3'>heavy extracellular domain</scene> which is part of the headpiece of the integrin. | The '''αIIb subunit''' (glycoprotein IIb) is composed of 1008 amino acids unevenly distributed over 2 chains. A part forms a light chain which comports a cytoplasmic tail of 20 amino acids and a transmembrane helix. An extracellular disulfide segment links this chain to the <scene name='80/802667/Alpha_head/3'>heavy extracellular domain</scene> which is part of the headpiece of the integrin. | ||
The extracellular N-Terminus forms a cap over the '''β-propeller''' domain which is folded by seven successive blades of aminoterminal repeats. Each blade is a β-hairpin loop-like structure composed of 4 antiparallel β strands located in each repeat and connected by loops of the surface. This β-propeller is linked to a '''thigh''' and '''two calf''' domains, which form the leg structure that supports the heavy head. The total forms the stalk of the αIIb subunit. The knee of the subunit between the thigh and the first calf domain is the site at which the head bends (inactivated form of the integrin. | The extracellular N-Terminus forms a cap over the '''β-propeller''' domain which is folded by seven successive blades of aminoterminal repeats. Each blade is a β-hairpin loop-like structure composed of 4 antiparallel β strands located in each repeat and connected by loops of the surface. This β-propeller is linked to a '''thigh''' and '''two calf''' domains, which form the leg structure that supports the heavy head. The total forms the stalk of the αIIb subunit. The knee of the subunit between the thigh and the first calf domain is the site at which the head bends (inactivated form of the integrin). | ||
The β-propeller hosts multiple '''cation biding sites'''. The last 3 or 4 blades bind <scene name='80/802667/Ca_ions_on_beta-propeller/4'>Ca2+ ions</scene> which influence ligand binding on the lower side of the blades and play an important role in biogenesis and stability of the heterodimer. The '''I domain''' inserted between blades 2 and 3 in the β-propeller follows a Rossman fold with five β-sheets surrounded by seven α-helices. Ligand binding occurs between the β-propeller and the β I domain of the β3 subunit via a coordinating '''Mg2+ ion''' in the MIDAS of the β3 subunit. | The β-propeller hosts multiple '''cation biding sites'''. The last 3 or 4 blades bind <scene name='80/802667/Ca_ions_on_beta-propeller/4'>Ca2+ ions</scene> which influence ligand binding on the lower side of the blades and play an important role in biogenesis and stability of the heterodimer. The '''I domain''' inserted between blades 2 and 3 in the β-propeller follows a Rossman fold with five β-sheets surrounded by seven α-helices. Ligand binding occurs between the β-propeller and the β I domain of the β3 subunit via a coordinating '''Mg2+ ion''' in the MIDAS of the β3 subunit. | ||
