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From Proteopedia
Crystal structure of a chimeric acetylcholine binding protein from Aplysia Californica (Ac-AChBP) containing the main immunogenic region (MIR) from the human alpha 1 subunit of the muscle nicotinic acetylcholine receptor in complex with anatoxin-A.
Structural highlights
DiseaseACHA_HUMAN Postsynaptic congenital myasthenic syndromes;Lethal multiple pterygium syndrome. The disease is caused by mutations affecting the gene represented in this entry. The alpha subunit is the main focus for antibody binding in myasthenia gravis. Myasthenia gravis is characterized by sporadic muscular fatigability and weakness, occurring chiefly in muscles innervated by cranial nerves, and characteristically improved by cholinesterase-inhibiting drugs. The disease is caused by mutations affecting the gene represented in this entry. The disease is caused by mutations affecting the gene represented in this entry. FunctionQ8WSF8_APLCA ACHA_HUMAN After binding acetylcholine, the AChR responds by an extensive change in conformation that affects all subunits and leads to opening of an ion-conducting channel across the plasma membrane. Publication Abstract from PubMedThe main immunogenic region (MIR) is a conformation-dependent region at the extracellular apex of alpha1 subunits of muscle nicotinic acetylcholine receptor (AChR) that is the target of half or more of the autoantibodies to muscle AChRs in human myasthenia gravis and rat experimental autoimmune myasthenia gravis. By making chimeras of human alpha1 subunits with alpha7 subunits, both MIR epitopes recognized by rat mAbs and by the patient-derived human mAb 637 to the MIR were determined to consist of two discontiguous sequences, which are adjacent only in the native conformation. The MIR, including loop alpha1 67-76 in combination with the N-terminal alpha helix alpha1 1-14, conferred high-affinity binding for most rat mAbs to the MIR. However, an additional sequence corresponding to alpha1 15-32 was required for high-affinity binding of human mAb 637. A water soluble chimera of Aplysia acetylcholine binding protein with the same alpha1 MIR sequences substituted was recognized by a majority of human, feline, and canine myasthenia gravis sera. The presence of the alpha1 MIR sequences in alpha1/alpha7 chimeras greatly promoted AChR expression and significantly altered the sensitivity to activation. This reveals a structural and functional, as well as antigenic, significance of the MIR. Main immunogenic region structure promotes binding of conformation-dependent myasthenia gravis autoantibodies, nicotinic acetylcholine receptor conformation maturation, and agonist sensitivity.,Luo J, Taylor P, Losen M, de Baets MH, Shelton GD, Lindstrom J J Neurosci. 2009 Nov 4;29(44):13898-908. doi: 10.1523/JNEUROSCI.2833-09.2009. PMID:19890000[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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Categories: Aplysia californica | Homo sapiens | Large Structures | Bobango J | Lindsatrom J | Luo J | Park JF | Talley TT | Taylor P | Wu J
