Figure 2.

Quantitative proteomic comparison of immunoisolated VGLUT-1- and VGAT-specific SVs reveals only few differences. Immunoisolated fractions were digested by trypsin and labeled with iTRAQ 114 or 115, respectively. The labeled peptides were first fractionated by SCX and subsequently analyzed by reverse phase liquid chromatography tandem mass spectrometry (LC-MS/MS). A–C, A total of 460 proteins were quantified in our study (supplemental Table 1, available at www.jneurosci.org as supplemental material), including vesicular transporters and ion channels (A) and trafficking and SV membrane proteins (B, C). Dotted lines indicate a ratio of 1, i.e., no difference between the two vesicle populations. Proteins identified to be significantly differentially expressed include in addition to the transporters VGLUT-1 and VGAT, the zinc transporter ZnT3, the vesicle membrane proteins SV2B, SV2C, SV31, synaptophysin, several synaptotagmin isoforms, the SNARE syntaxin 1a, and MAL2, a novel SV protein.