2cm5
crystal structure of the C2B domain of rabphilin
Structural highlights
FunctionRP3A_RAT Protein transport. Probably involved with Ras-related protein Rab-3A in synaptic vesicle traffic and/or synaptic vesicle fusion. Could play a role in neurotransmitter release by regulating membrane flow in the nerve terminal. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedThe Ca(2+) binding properties of C2 domains are essential for the function of their host proteins. We present here the first crystal structures showing an unexpected Ca(2+) binding mode of the C2B domain of rabphilin-3A in atomic detail. Acidic residues from the linker region between the C2A and C2B domains of rabphilin-3A interact with the Ca(2+)-binding region of the C2B domain. Because of these interactions, the coordination sphere of the two bound Ca(2+) ions is almost complete. Mutation of these acidic residues to alanine resulted in a 10-fold decrease in the intrinsic Ca(2+) binding affinity of the C2B domain. Using NMR spectroscopy, we show that this interaction occurred only in the Ca(2+)-bound state of the C2B domain. In addition, this Ca(2+) binding mode was maintained in the C2 domain tandem fragment. In NMR-based liposome binding assays, the linker was not released upon phospholipid binding. Therefore, this unprecedented Ca(2+) binding mode not only shows how a C2 domain increases its intrinsic Ca(2+) affinity, but also provides the structural base for an atypical protein-Ca(2+)-phospholipid binding mode of rabphilin-3A. The C2A-C2B linker defines the high affinity Ca(2+) binding mode of rabphilin-3A.,Montaville P, Schlicker C, Leonov A, Zweckstetter M, Sheldrick GM, Becker S J Biol Chem. 2007 Feb 16;282(7):5015-25. Epub 2006 Dec 13. PMID:17166855[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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