UNASSIGNED: Secretory proteins traffic from endoplasmic reticulum (ER) to Golgi via the coat protein complex II (COPII) vesicle, which consists of five cytosolic components ( @entity61500 , Sec23-24, and Sec13-31). In eukaryotes, COPII transport has diversified due to gene duplication, creating multiple COPII paralogs. Evidence has accumulated, revealing the functional heterogeneity of COPII paralogs in protein ER export. @entity68817 , the small GTPase of COPII machinery, seems to be specialized for large cargo secretion in mammals. @entity958 contains five @entity61500 and seven Sec23 homologs, and AtSar1a was previously shown to exhibit different effects on a-amylase secretion. However, mechanisms underlying the functional diversity of @entity61500 paralogs remain unclear in higher organisms. Here, we show that the @entity958 @entity61500 homolog AtSar1a exhibits distinct localization in plant cells. Transgenic @entity958 plants expressing dominant-negative AtSar1a exhibit distinct effects on ER cargo export. Mutagenesis analysis identified a single @entity3689 , @entity2569 84, as being responsible for the functional diversity of AtSar1a. Structure homology modeling and interaction studies revealed that @entity2569 84 is crucial for the specific interaction of AtSar1a with AtSec23a, a distinct @entity958 Sec23 homolog. Structure modeling and coimmunoprecipitation further identified a corresponding @entity3689 , @entity2569 484, on AtSec23a as being essential for the specific pair formation. At the cellular level, the @entity2569 484 mutation affects the distinct function of AtSec23a on vacuolar cargo trafficking. Additionally, dominant-negative AtSar1a affects the ER export of the transcription factor @entity68818 under ER stress. We have demonstrated a unique plant pair of COPII machinery function in ER export and the mechanism underlying the functional diversity of COPII paralogs in eukaryotes.

Unique COPII component AtSar1a/AtSec23a pair is required for the distinct function of protein ER export in XXXX .

@entity68817 :: ('842086(Tax:3702)', 'Gene') :: ['Sar1B'] @entity958 :: ('3702', 'Species') :: ['Arabidopsis'] @entity2569 :: ('CHEBI:17561', 'Chemical') :: ['Cys'] @entity68818 :: ('820249(Tax:3702)', 'Gene') :: ['bZIP28'] @entity61500 :: ('817874(Tax:3702)', 'Gene') :: ['Sar1'] @entity3689 :: ('D000596', 'Chemical') :: ['amino acid']
@entity958 :: (3702,Species) :: ['Arabidopsis thaliana']
