The C-terminal dilysine motif confers endoplasmic reticulum localization to type I membrane proteins in plants

Citation
M. Benghezal et al., The C-terminal dilysine motif confers endoplasmic reticulum localization to type I membrane proteins in plants, PL CELL, 12(7), 2000, pp. 1179-1201
Citations number
99
Categorie Soggetti
Plant Sciences","Animal & Plant Sciences
Journal title
PLANT CELL
ISSN journal
10404651 → ACNP
Volume
12
Issue
7
Year of publication
2000
Pages
1179 - 1201
Database
ISI
SICI code
1040-4651(200007)12:7<1179:TCDMCE>2.0.ZU;2-4
Abstract
The tomato Cf-9 disease resistance gene encodes a type I membrane protein c arrying a cytosolic dilysine motif. In mammals and yeast, this motif promot es the retrieval of type I membrane proteins from the Golgi apparatus to th e endoplasmic reticulum (ER). To test whether the C-terminal KKXX signal of Cf-9 is functional as a retrieval motif and to investigate its role in pla nts, green fluorescent protein (GFP) was fused to the transmembrane domain of Cf-9 and expressed in yeast, Arabidopsis, and tobacco cells. The fusion protein was targeted to the ER in each of these expression systems, and mut ation of the KKXX motif to NNXX led to secretion of the fusion protein. In yeast, the mutant protein reached the vacuole, but plants secreted it as a soluble protein after proteolytic removal of the transmembrane domain. Trip le hemagglutinin (HA)-tagged full-length Cf-9 was also targeted to the ER i n tobacco cells, and cleavage was also observed for the NNXX mutant protein , suggesting an endoprotease recognition site located within the Cf-9 lumen al sequence common to both the GFP- and the HA-tagged fusions. Our results indicate that the KKXX motif confers ER localization in plants as well as m ammals and yeast and that Cf-9 is a resident protein of the ER.