The calcium-dependent and calcium-independent membrane binding of synaptotagmin 1: two modes of C2B binding.

ABSTRACT: The Ca2+-independent membrane interactions of the soluble C2 domains from synaptotagmin 1 (syt1) were characterized using a combination of site-directed spin labeling and vesicle sedimentation. The second C2 domain of syt1, C2B, binds to membranes containing phosphatidylserine and phosphatidylcholine in a Ca2+-independent manner with a lipid partition coefficient of approximately 3.0 x 10(2) M(-1). A soluble fragment containing the first and second C2 domains of syt1, C2A and C2B, has a similar affinity, but C2A alone has no detectable affinity to phosphatidylcholine/phosphatidylserine bilayers in the absence of Ca2+. Although the Ca2+-independent membrane affinity of C2B is modest, it indicates that this domain will never be free in solution within the cell. Site-directed spin labeling wa

SUBMITTER: Kuo W 

PROVIDER: S-EPMC2669496 | biostudies-literature | 2009 Mar

REPOSITORIES: biostudies-literature