A: Sequence for human GRP78 precursor, with peptides identified by MALDI-MS in spots 21–24 labeled as follows: solid line, peptides seen in spots 21–23; dashed line, peptides seen in 21 and 24; dash-dot, peptide seen in 21 only; dotted lines, missed cleavages seen in 22–24. Shaded sequence is signal peptide at N-terminal, and shaded Q409 is boundary between N- and C-terminal domains. B: MALDI spectra of GRP78 spots 21 (full-length), 23 (N-terminal domain), and 24 (C-terminal domain). Peaks are labeled with residue numbers, with those from the C-terminal domain labeled in italics, and tryptic missed cleavage peptides in spectra 23 and 24 underlined. T denotes trypsin autolysis peaks.