Subclass‐Specific Localization and Trafficking of A rabidopsis p 24 Proteins in the ER – G olgi Interface

We describe a comprehensive analysis of the subcellular localization and in vivo trafficking of A rabidopsis p 24 proteins. In A rabidopsis, there are 11 p 24 proteins, which fall into only δ and β subfamilies. Interestingly, the δ subfamily of p 24 proteins in A rabidopsis is elaborated spectacularly in evolution, which can be grouped into two subclasses: p 24δ1 and p 24δ2. We found that, although all p 24δ proteins possess classic COPII / COPI binding motifs in their cytosolic C ‐termini, p 24δ1 proteins are localized to the endoplasmic reticulum ( ER ), p 24δ2 proteins are localized to both ER and G olgi. Two p 24β proteins reside largely in G olgi. Similar to Atp 24 (termed p 24δ1 c in this study), p 24δ2 d also cycles between the ER and G olgi. Interestingly, coexpression with p 24β1 could retain p 24δ2 d , but not p 24δ1 d in G olgi. We revealed that the lumenal coiled‐coil domain of p 24δ2 d is required for its steady‐state localization in G olgi, probably through its interaction with p 24β1. In p 24β1, there is no classic COPII or COPI binding motif in its C ‐terminus. However, the protein also cycles between the ER and G olgi. We found that a conserved RV motif located at the extreme end of the C ‐terminus of p 24β1 plays an important role in its G olgi target.