The C-TERMINUS of AtGRIP Is Crucial for Its Self-Association and for Targeting to Golgi Stacks in Arabidopsis

BACKGROUND In animals and fungi, dimerization is crucial for targeting GRIP domain proteins to the Golgi apparatus. Only one gene in the Arabidopsis genome, AtGRIP, codes for a GRIP domain protein. It remains unclear whether AtGRIP has properties similar to those of GRIP domain proteins. RESULTS In this study, western blot and yeast two-hybrid analyses indicated that AtGRIPs could form a parallel homodimer. In addition, yeast two-hybrid analysis indicated that AtGRIPaa711-753, AtGRIPaa711-766 and AtGRIPaa711-776 did not interact with themselves, but the intact GRIP domain with the AtGRIP C-terminus did. Confocal microscopy showed that only an intact GRIP domain with an AtGRIP C-terminus could localize to the Golgi stacks in Arabidopsis leaf protoplasts. A BLAST analysis showed that the C-terminus of GRIP proteins was conserved in the plant kingdom. Mutagenesis and yeast two-hybrid analyses showed that the L742 of AtGRIP contributed to dimerization and was crucial for Golgi localization. CONCLUSIONS These results indicate that the C-terminus of GRIP proteins is essential for self-association and for targeting of Golgi stacks in plant cells. We suggest that several properties of GRIP proteins differ between plant and animal cells.