Structure and Ca²?-binding properties of the tandem C? domains of E-Syt2.

ABSTRACT: Contacts between the endoplasmic reticulum and the plasma membrane involve extended synaptotagmins (E-Syts) in mammals or tricalbins in yeast, proteins with multiple C? domains. One of the tandem C? domains of E-Syt2 is predicted to bind Ca²?, but no Ca²?-dependent function has been attributed to this protein. We have determined the crystal structures of the tandem C? domains of E-Syt2 in the absence and presence of Ca²? and analyzed their Ca²?-binding properties by nuclear magnetic resonance spectroscopy. Our data reveal an unexpected V-shaped structure with a rigid orientation between the two C? domains that is not substantially altered by Ca²?. The E-Syt2 C2A domain binds up to four Ca²? ions, whereas the C?B domain does not bind Ca²?. These results suggest that E-Syt2 performs an as yet unidentified Ca²?-dependent function through its C?A domain and uncover fundamental differences between the properties of the tandem C? domains of E-Syts and synaptotagmins.

SUBMITTER: Xu J 

PROVIDER: S-EPMC3946263 | biostudies-literature | 2014 Feb

REPOSITORIES: biostudies-literature