Molecular characterization of a vacuolar processing enzyme related to a putative cysteine proteinase of Schistosoma mansoni.
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.
Hara-Nishimura
I
I
Department of Cell Biology, National Institute for Basic Biology, Okazaki, Japan.
Takeuchi
Y
Y
Nishimura
M
M
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002367:Ricinus communis / Q000201:enzymology* / Q000235:genetics; D003546:Cysteine Endopeptidases / Q000096:biosynthesis / Q000235:genetics*; D004792:Enzyme Precursors / Q000235:genetics; D008969:Molecular Sequence Data; D010947:Plants, Toxic; D012323:RNA Processing, Post-Transcriptional; D012550:Schistosoma mansoni / Q000201:enzymology* / Q000235:genetics; D014617:Vacuoles / Q000201:enzymology*
D004792:Enzyme Precursors; D003546:Cysteine Endopeptidases