Fig. 2

Mass spectrometry analysis of the PS1 interacting proteins. a Coomassie-stained gel of the proteins eluted from the column. The gel slices with bands of different sizes were excised from the Ca²⁺ (+) and Ca²⁺ (-) condition from the GST-PS1 pull-downs, and were sent for mass spectrometry analysis (indicated by lines to the right of the gel). The slice selection was based on the differences in the protein profiles/band intensities between GST-control and GST-PS1 pull-down, GST-PS1 pull-down from brain lysates vs. lysis buffer, and between Ca²⁺ (+) and Ca²⁺ (-) condition (these bands are indicated with the asterisks). The bands containing Syt1 are indicated with arrowheads. Three independent MS screens were performed. The Table shows number of peptides identified and the sequence coverage for Syt1 in Ca²⁺ (-) and Ca²⁺ (+) conditions; catenin1 delta is shown as Ca²⁺-independent control. b Image of the coomassie stained gel from a different MS experiment shows differences in the band intensities for proteins pulled down with the GST-PS1 L6-7 (the area is overexposed in Fig. 2a). The arrowhead points to the band containing Syt1. c Schematic representation of the PS1 molecule and the GST-fusion peptides used in the MS screen of the Triton X-100-digested mouse brain lysates for PS1-binding partners; gray cylinders correspond to PS1 transmembrane domains. PS1 fragments used in the pull-down are labeled in red, green and blue. PS1 presenilin 1, GST glutathione S-transferase, Syt1 synaptotagmin 1, MS mass spectrometry