RT Journal Article
SR Electronic
T1 Molecular characterization of a vacuolar processing enzyme related to a putative cysteine proteinase of Schistosoma mansoni.
JF The Plant Cell
JO Plant Cell
FD American Society of Plant Biologists
SP 1651
OP 1659
DO 10.1105/tpc.5.11.1651
VO 5
IS 11
A1 Hara-Nishimura, I
A1 Takeuchi, Y
A1 Nishimura, M
YR 1993
UL http://www.plantcell.org/content/5/11/1651.abstract
AB Proproteins of various vacuolar proteins are post-translationally processed into mature forms by the action of a unique vacuolar processing enzyme. If such a processing enzyme is transported to vacuoles together with proprotein substrates, the enzyme must be a latent form. Immunocytochemical localization of a vacuolar processing enzyme, a 37-kD cysteine proteinase, in the endosperm of maturing castor bean seeds places the enzyme in the vacuolar matrix, where a variety of proproteins is also present. To characterize a molecular structure of vacuolar processing enzyme, we isolated a cDNA for the enzyme. Deduced primary structure of a 55-kD precursor is 33% identical to a putative cysteine proteinase of the human parasite Schistosoma mansoni. The precursor is composed of a signal peptide, a 37-kD active processing enzyme domain, and a propeptide fragment. Although the precursor expressed in Escherichia coli has no vacuolar processing activity, a 36-kD immunopositive protein expressed in E. coli is active. These results suggest that the activation of the vacuolar processing enzyme requires proteolytic cleavage of a 14-kD C-terminal propeptide fragment of the precursor.