2cm6: Difference between revisions

The 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.

2CM6 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Rattus_norvegicus Rattus norvegicus] with CA and PO4 as [http://en.wikipedia.org/wiki/ligands ligands]. Structure known Active Site: AC1. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=2CM6 OCA].  

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