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Arabidopsis has Two Functional Orthologs of the Yeast V‐ATPase Assembly Factor Vma21p
Author(s) -
Neubert Christoph,
Graham Laurie A.,
BlackMaier Eric W.,
Coonrod Emily M.,
Liu TzuYin,
Stierhof YorkDieter,
Seidel Thorsten,
Stevens Tom H.,
Schumacher Karin
Publication year - 2008
Publication title -
traffic
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.677
H-Index - 130
eISSN - 1600-0854
pISSN - 1398-9219
DOI - 10.1111/j.1600-0854.2008.00799.x
Subject(s) - biology , arabidopsis , endoplasmic reticulum , golgi apparatus , microbiology and biotechnology , chaperone (clinical) , saccharomyces cerevisiae , yeast , atpase , protein subunit , biochemistry , mutant , gene , enzyme , medicine , pathology
How individual protein subunits assemble into the higher order structure of a protein complex is not well understood. Four proteins dedicated to the assembly of the V 0 subcomplex of the V‐adenosine triphosphatase (V‐ATPase) in the endoplasmic reticulum (ER) have been identified in yeast, but their precise mode of molecular action remains to be identified. In contrast to the highly conserved subunits of the V‐ATPase, orthologs of the yeast assembly factors are not easily identified based on sequence similarity. We show in this study that two ER‐localized Arabidopsis proteins that share only 25% sequence identity with Vma21p can functionally replace this yeast assembly factor. Loss of AtVMA21a function in RNA interference seedlings caused impaired cell expansion and changes in Golgi morphology characteristic for plants with reduced V‐ATPase activity, and we therefore conclude that AtVMA21a is the first V‐ATPase assembly factor identified in a multicellular eukaryote. Moreover, VMA21p acts as a dedicated ER escort chaperone, a class of substrate‐specific accessory proteins so far not identified in higher plants.