SDS/PAGE and Immunoblot Analysis. Protein samples
from various steps in the purification process were separated
on an 8-25% gradient PhastGel (Pharmacia) and detected by
the silver staining. For immunoblot analysis, samples were
separated by SDS/PAGE on a 10% gel, transferred to nitrocellulose,
and reacted with antisera for N-terminal (aa 6-19)
or C-terminal (aa 382-400) peptides of human calreticulin.
Amino Acid Sequencing. Approximately 1 nmol of HPECpurified
protein was digested with sequencing grade trypsin
(Promega) for 12 hr. The tryptic peptides were purified on a