Table 2.

Analysis of Starch Granule–Associated Polypeptides from T. aestivum Endosperm Amyloplasts by Q-TOF-MS

Phosphorylated Starch Granule–Associated PolypeptidesQ-TOF-MS–Derived SequenceIdentity of Protein
120 kD(R)YGDYEEAYDVGVRSS (fragment)
88-kD phosphoproteins cross-reacting with anti-SBEIIa and anti-SBEIIb antisera(R)AAIDQHEGGLEAFSR (R)DDYGVWEIFLPNNADGSSAIPHGSR (K)INSYANFRDEVLPR (R)GPQTLPTGK (K)VALDSDDALFGGFSRSBEIIa and/or SBEIIb
85 kD(K)A248LSPPAAPAVQQDLWDFKKYIGFEEPVEAKDDGR281 (K)T322GGLGDVAGALPK334 (R)H396RQEDIYGGSR406 (R)G483PVDEFPFTELPEHYLEHFRLYDPVGGEHANYFAAGLK520 (K)L786YEDVLVK793SSIIa (wSSII-B)
Nonphosphorylated 152-kD polypeptide cross-reacting with anti-SBEI antiserum(K)F129GINTENDATVYR142 (K)D150AQLIGDFNNWNGSGHR166 (K)D170NFGVWSIRISHVNGKPAIPHNSK193 (K)F223GAPYDGVHWDPPTGER239 (R)S482VDEGGVGFDYR493SBEIc
  • Silver-stained polypeptides were excised from polyacrylamide gels (Figure 3) and digested with trypsin, and the recovered peptides were sequenced using Q-TOF-MS to identify the phosphoproteins and other polypeptides. The peptide sequences presented for each polypeptide analyzed were acquired from a single representative in-gel digest and, where applicable, show their position within the sequence of the presumptive unprocessed protein. The presence of Gln259 and Val792 in the peptide sequences from SSIIa are shown in bold.