CALRETICULIN IS THE MAJOR CA2-RETICULUM OF THE PEA PLANT (PISUM-SATIVUM)( STORAGE PROTEIN IN THE ENDOPLASMIC)

A 56kDa protein with high similarity in its N-terminal amino acid sequ ence to animal calreticulin and 100% homology with the N-terminal amin o acids of spinach calreticulin has been identified in seeds of the pe a plant (Pisum sativum). A new purification procedure is described by which the calreticulin-like protein was selectively solubilized by inc ubation with deoxycholate and HgCl2 from microsomes enriched for endop lasmic reticulum. Following Mono Q ion exchange chromatography of the deoxycholate extract by fast protein liquid chromatography, the calret iculin-like protein was obtained in nearly pure form. This purified pr otein is similar to animal calreticulin in apparent mass, characterist ic blue staining with Stains-all dye and calcium-binding ability. In a ddition, this protein is recognized only by affinity purified antibodi es against rabbit calreticulin and is not recognized by anti-calseques trin antibodies. Our data suggested that calreticulin rather than cals equestrin functions as the Ca2+-storage protein in the endoplasmic ret iculum of pea plants. (C) 1995 Academic Press, Inc.