Download MendeleyStructural Determinants for Ca2+ and Phosphatidylinositol 4,5-Bisphosphate Binding by the C2A Domain of Rabphilin-3A.
Coudevylle, N., Montaville, P., Leonov, A., Zweckstetter, M., Becker, S.(2008) J Biol Chem 283: 35918-35928
- PubMed: 18945677
- DOI: https://doi.org/10.1074/jbc.M804094200
- Primary Citation of Related Structures:
2K3H - PubMed Abstract:
Rabphilin-3A is a neuronal C2 domain tandem containing protein involved in vesicle trafficking. Both its C2 domains (C2A and C2B) are able to bind phosphatidylinositol 4,5-bisphosphate, a key player in the neurotransmitter release process. The rabphilin-3A C2A domain has previously been shown to bind inositol-1,4,5-trisphosphate (IP3; phosphatidylinositol 4,5-bisphosphate headgroup) in a Ca2+-dependent manner with a relatively high affinity (50 microm) in the presence of saturating concentrations of Ca2+. Moreover, IP3 and Ca2+ binding to the C2A domain mutually enhance each other. Here we present the Ca2+-bound solution structure of the C2A domain. Structural comparison with the previously published Ca2+-free crystal structure revealed that Ca2+ binding induces a conformational change of Ca2+ binding loop 3 (CBL3). Our IP3 binding studies as well as our IP3-C2A docking model show the active involvement of CBL3 in IP3 binding, suggesting that the conformational change on CBL3 upon Ca2+ binding enables the interaction with IP3 and vice versa, in line with a target-activated messenger affinity mechanism. Our data provide detailed structural insight into the functional properties of the rabphilin-3A C2A domain and reveal for the first time the structural determinants of a target-activated messenger affinity mechanism.
Organizational Affiliation:
Department of NMR-based Structural Biology, Max-Planck-Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany.
