7k6b
From Proteopedia
Solution Structure of the Dysferlin C2A Domain in its Calcium-free State
Structural highlights
DiseaseDYSF_HUMAN Miyoshi myopathy;Distal myopathy with anterior tibial onset;Congenital myopathy, Paradas type;Autosomal recessive limb-girdle muscular dystrophy type 2B. 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. The disease is caused by mutations affecting the gene represented in this entry. FunctionDYSF_HUMAN Key calcium ion sensor involved in the Ca(2+)-triggered synaptic vesicle-plasma membrane fusion. Plays a role in the sarcolemma repair mechanism of both skeletal muscle and cardiomyocytes that permits rapid resealing of membranes disrupted by mechanical stress (By similarity). Publication Abstract from PubMedThe membrane protein dysferlin (DYSF) is important for calcium-activated plasma membrane repair, especially in muscle fibre cells. Nearly 600 mutations in the DYSF gene have been identified that are causative for rare genetic forms of muscular dystrophy. The dysferlin protein consists of seven C2 domains (C2A-C2G, 13%-33% identity) used to recruit calcium ions and traffic accessory proteins and vesicles to injured membrane sites needed to reseal a wound. Amongst these, the C2A is the most prominent facilitating the calcium-sensitive interaction with membrane surfaces. In this work, we determined the calcium-free and calcium-bound structures of the dysferlin C2A domain using NMR spectroscopy and X-ray crystallography. We show that binding two calcium ions to this domain reduces the flexibility of the Ca2+-binding loops in the structure. Furthermore, calcium titration and mutagenesis experiments reveal the tight coupling of these calcium-binding sites whereby the elimination of one site abolishes calcium binding to its partner site. We propose that the electrostatic potential distributed by the flexible, negatively charged calcium-binding loops in the dysferlin C2A domain control first contact with calcium that promotes subsequent binding. Based on these results, we hypothesize that dysferlin uses a 'calcium-catching' mechanism to respond to calcium influx during membrane repair. Calcium binds and rigidifies the dysferlin C2A domain in a tightly coupled manner.,Wang Y, Tadayon R, Santamaria L, Mercier P, Forristal CJ, Shaw GS Biochem J. 2021 Jan 15;478(1):197-215. doi: 10.1042/BCJ20200773. PMID:33449082[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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