Table II

BEMAD identifies previously mapped sites of O-GlcNAc on Synapsin I

Rat brain Synapsin I tryptic peptides identified from LC-MS/MS after BEMAD. Turbosequest software was used to search MS/MS spectrums obtained on an LCQ ion trap mass spectrometer against a non-redundant fasta data base containing over 500,000 protein entries. Shown are the top ranked peptides derived from analysis before and after enrichment by thiol chromatography. # or * following serine or threonine denotes mass addition at that site of 136.2 daltons, indicating modification by DTT. Underlined peptides contain DTT-modified sites previously identified as O-GlcNAc modified. z, charge state of ion; Xcorr, sequest confidence score for peptide identification.

zPredicted MH+Observed MH+XcorrMatched ionsProteinPeptide sequence
Prior to enrichment by thiol chromatography
21726.51725.93.7821 /30Syn I ratTNTGSAMLEQIAMSDR
31562.91562.73.1529 /60Syn I ratGSHSQTPSPGALPLGR
21053.71053.23.1214 /20Syn I ratQASISGPAPPK
22151.22150.43.0315 /34Syn I ratLGTEEFPLIDQTFYPNHK
2816.8817.02.907 /12Syn I ratMTQALPR
2879.7878.92.8211 /14Syn I ratTSVSGNWK
1924.7925.02.608 /14Syn I ratIHGEIDIK
22189.02188.52.5616 /44Syn I ratQTTAAAAATFSEQVGGG(S*)GGAGR
After enrichment by thiol chromatography
22189.02188.54.0525 /44Syn I ratQ(T#)TAAAAATFSEQVGGGSGGAGR
21699.31698.33.1022 /30Syn I ratG(S*)HSQTPSPGALPLGR
21591.31590.32.5012 /24Syn I ratEMLS(S*)TTYPVVVK
11590.31590.32.4214 /24Syn I ratEMLS(S*)TTYPVVVK
22189.02188.52.4914 /44Syn I ratQTTAAAAATF(S*)EQVGGGSGGAGR
22189.02188.41.9714 /44Syn I ratQTTAAAAATFSEQVGGG(S*)GGAGR
22547.22546.21.8812 /46Syn I ratLPSPTAAPQQ(S*)ASQATPMTQGQGR