POSTTRANSLATIONAL PROCESSING OF A CARBOXY-TERMINAL PROPEPTIDE CONTAINING A KDEL SEQUENCE OF PLANT VACUOLAR CYSTEINE ENDOPEPTIDASE (SH-EP)

A plant cysteine endopeptidase, designated SH-EP, is a major protease occurring in cotyledons of Vigna mungo seedlings, and acts to degrade seed globulin stored in protein bodies. Here we show that the 43 kDa intermediate of SH-EP formed in the endoplasmic reticulum is transported to protein bodies and processed to the 33 kDa mature form during transport or thereafter, and that the COOH-terminal propeptide of 10 amino acid residues containing a KDEL sequence, which is known as a retention signal for the endoplasmic reticulum lumen, is processed to form the mature SH-EP.