Table 2.

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

Phosphorylated Starch Granule–Associated Polypeptides	Q-TOF-MS–Derived Sequence	Identity of Protein
120 kD	(R)YGDYEEAYDVGVR	SS (fragment)
88-kD phosphoproteins cross-reacting with anti-SBEIIa and anti-SBEIIb antisera	(R)AAIDQHEGGLEAFSR (R)DDYGVWEIFLPNNADGSSAIPHGSR (K)INSYANFRDEVLPR (R)GPQTLPTGK (K)VALDSDDALFGGFSR	SBEIIa and/or SBEIIb
85 kD	(K)A248LSPPAAPAVQQDLWDFKKYIGFEEPVEAKDDGR281 (K)T322GGLGDVAGALPK334 (R)H396RQEDIYGGSR406 (R)G483PVDEFPFTELPEHYLEHFRLYDPVGGEHANYFAAGLK520 (K)L786YEDVLVK793	SSIIa (wSSII-B)
Nonphosphorylated 152-kD polypeptide cross-reacting with anti-SBEI antiserum	(K)F129GINTENDATVYR142 (K)D150AQLIGDFNNWNGSGHR166 (K)D170NFGVWSIRISHVNGKPAIPHNSK193 (K)F223GAPYDGVHWDPPTGER239 (R)S482VDEGGVGFDYR493	SBEIc

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.