Nature Structural & Molecular Biology11, 45 - 53 (2003)
Published online: 29 December 2003; | doi:10.1038/nsmb707
A conformational switch in the Piccolo C2A domain regulated by alternative splicing
Jesus Garcia1, 3, 4, Stefan H Gerber2, 3, 4, Shuzo Sugita2, 3, Thomas C Südhof2
& Josep Rizo1
1
Departments of Biochemistry and Pharmacology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, Texas 75390, USA.
2
Center for Basic Neuroscience, Department of Molecular Genetics, and Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, Texas 75390, USA.
3
Present addresses: RMN de Biomolecules, Parc Cientific de Barcelona, Barcelona 08028, Spain (J.G.); Universitatsklinik Heidelberg Street, Heidelberg, M5T 1B3, Germany (S.H.G.) and Division of Cellular and Molecular Biology, Toronto Western Research Institute, 69120, Ontario, Canada (S.S.).
C2 domains are widespread Ca2+-binding modules. The active zone protein Piccolo (also known as Aczonin) contains an unusual C2A domain that exhibits a low affinity for Ca2+, a Ca2+-induced conformational change and Ca2+-dependent dimerization. We show here that removal of a nine-residue sequence by alternative splicing increases the Ca2+ affinity, abolishes the conformational change and abrogates dimerization of the Piccolo C2A domain. The NMR structure of the Ca2+-free long variant provides a structural basis for these different properties of the two splice forms, showing that the nine-residue sequence forms a -strand otherwise occupied by a nonspliced sequence. Consequently, Ca2+-binding to the long Piccolo C2A domain requires a marked rearrangement of secondary structure that cannot occur for the short variant. These results reveal a novel mechanism of action of C2 domains and uncover a structural principle that may underlie the alteration of protein function by short alternatively spliced sequences.
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-strand otherwise occupied by a nonspliced sequence. Consequently, Ca2+-binding to the long Piccolo C2A domain requires a marked rearrangement of secondary structure that cannot occur for the short variant. These results reveal a novel mechanism of action of C2 domains and uncover a structural principle that may underlie the alteration of protein function by short alternatively spliced sequences.
