2 SYNAPTIC VESICLE PROTEINS OF 25 KDA - A COMPARISON OF THE MOLECULAR-PROPERTIES AND TISSUE DISTRIBUTION OF SVP25 AND O-RAB3

Two synaptic vesicle proteins of the electric ray Torpedo-svp25 and o- rab3-are compared with respect to their biochemical properties and tis sue distribution. On SDS-PAGE both proteins migrate to the same positi on of about 25 kDa. As revealed by application of monospecific antibod ies and subcellular fractionation both proteins comigrate and cofracti onate with the synaptic vesicle compartment. o-Rab3 and svp25 can be s eparated by lectin chromatography; svp25 is highly glycosylated and bi nds to concanavalin A sepharose. Upon deglycosylation using glycopepti dase F and O-glycosidase its apparent molecular mass is reduced to abo ut 14 kDa. Partial amino acid sequences obtained by direct microsequen cing of purified and deglycosylated svp25 revealed that svp25 is a nov el protein that has not yet been characterized in molecular terms. Whe reas svp25 was detected in all brain areas investigated, the expressio n of o-rab3 was found to be restricted to specific regions. An immunob lot analysis demonstrates an exclusive association of both proteins wi th neural tissues. Our results suggest that cholinergic synaptic vesic les from electric ray electric organ contain at least two membrane-ass ociated proteins of an apparent molecular mass of 25 kDa, the membrane associated o-rab3 and the membrane integral protein svp25. The two pr oteins can be separated by lectin chromatography for assessment of the ir biochemical properties.