Known secretory machine proteins that have not been detected in platelets. Platelet membrane extract (HPE) was immunochemically tested for the presence of known SNARE and SNARE-associated integral membrane proteins. HPE in the amounts of 50 and 200 μg was examined by SDS-PAGE, Western blotting, and probing with antibodies against VAMP-2, SNAP-25, synaptophysin, and synaptotagmin (see Materials and Methods). Fifty micrograms of detergent-solubilized bovine brain membrane extract (BBE) were analyzed in parallel as a positive control for these antisera. The immunoreactivities of these antibodies are given to the right of each blot: bovine (b), CHO cells (CHO), human (h), mouse (m) rat (r).