C-terminal KDEL sequence of a KDEL-tailed cysteine proteinase (sulfhydryl-endopeptidase) is involved in formation of KDEL vesicle and in efficient vacuolar transport of sulfhydryl-endopeptidase.
Sulfhydryl-endopeptidase (SH-EP) is a papain-type vacuolar proteinase expressed in cotyledons of germinated Vigna mungo seeds, and the enzyme possesses a C-terminal propeptide containing KDEL tail, an endoplasmic reticulum retention signal for soluble proteins. SH-EP is transported to vacuoles via a KDEL vesicle (KV) through a Golgi complex-independent route. To see the function of the KDEL sequence of SH-EP, wild-type SH-EP and its KDEL deletion mutant (SH-EPDeltaKDEL) were heterologously expressed in Arabidopsis and in cultured tobacco Bright Yellow 2 cells, and their intracellular transport pathways and localizations were analyzed. A combination of the results from analyses for transformed Arabidopsis and tobacco (Nicotiana tabacum) cells indicated that wild-type SH-EP is packed into KV-like vesicles through the KDEL sequence and is transported to vacuoles in the cells of transformants. In contrast, KV was not formed/induced in the cells expressing SH-EPDeltaKDEL, and the mutant protein was mainly secreted. Therefore, the C-terminal KDEL sequence of the KDEL-tailed cysteine proteinase is thought to be involved in the formation of KV, and in the efficient vacuolar transport of the proteins through KV.
Okamoto
Takashi
T
Department of Biological Sciences, Tokyo Metropolitan University, Hachioji, Tokyo, 192-0397 Japan. okamoto-takashi@c.metro-u.ac.jp
Shimada
Tomoo
T
Hara-Nishimura
Ikuko
I
Nishimura
Mikio
M
Minamikawa
Takao
T
D017360:Arabidopsis / Q000166:cytology / Q000235:genetics / Q000378:metabolism; D001692:Biological Transport; D002478:Cells, Cultured; D003546:Cysteine Endopeptidases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D009842:Oligopeptides / Q000235:genetics / Q000378:metabolism*; D010641:Phenotype; D030821:Plants, Genetically Modified; D011499:Protein Processing, Post-Translational; D021382:Protein Sorting Signals / Q000235:genetics; D017384:Sequence Deletion; D014026:Nicotiana / Q000166:cytology / Q000235:genetics / Q000378:metabolism; D014617:Vacuoles / Q000378:metabolism*
D009842:Oligopeptides; D021382:Protein Sorting Signals; C073762:lysyl-aspartyl-glutamyl-leucine; D003546:Cysteine Endopeptidases