Table 2.

Peptide Sequencing Identifies AG Peptides

SourcePeptide Backbone Sequence
4.9 minaX-X-A-O-A-O-S-O-T-Sb
AtAGP12T-E-A-O-A-O-S-O-T-Sc,d
AtAGP13V-E-A-O-A-O-S-O-T-Sc
AtAGP14V-D-A-O-A-O-S-O-T-Sc
AtAGP15S-E-A-O-A-O-S-O-T-S-G-Sc,d
AtAGP16S-L-A-O-A-O-A-O-T-Sc,d,e
  • a Peptide fraction from leaves with a retention time of 4.9 min (after deglycosylation and deblocking).

  • b Amino acids are represented by the single-letter code; X indicates very low signal such that no single amino acid residue could be distinguished. In the seventh cycle, Ser was the major amino acid residue and Ala was a minor component.

  • c Predicted mature peptide backbone assuming N- and C-terminal signals are removed and all Pro residues are modified to Hyp(O). Residues common to all sequences are in boldface type.

  • d The mature peptide backbone is predicted to begin with a glutamine residue. This residue is not shown because it would be removed from the peptide in the enzymatic deblocking step.

  • e The protein predicted by this clone includes a GPI anchor consensus cleavage site followed by a hydrophobic domain (see Figure 2C), but it is not predicted to be GPI-anchored based on PSORT prediction of cellular localization (Nakai and Horton, 1999). However, purification results suggest that AtAGP16 is likely to be GPI-anchored (see Discussion).