Abstract
Storage proteins are synthesized on ER as precursors and then are transported to protein storage vacuoles, where they are processed into mature forms. We isolated an Arabidopsis mutant (mag2) that accumulated precursors of 2S albumin and 12S globulin, in seeds (1). mag2 seed cells contained many novel structures with an electron-dense core composed of the precursors of 2S albumin. 12S globulins were localized in the matrix region of the structures together with ER chaperones, BiP and PDI, which were more abundant in mag2 seeds. MAG2 protein had a RINT-1/TIP20 domain in the C-terminal region. Some MAG2 molecules were peripherally associated with the ER membrane. MAG2 had an ability to bind to two ER-localized t-SNAREs (At-Sec20 and At-Ufe1). Our findings suggest that MAG2 functions in the transport of storage protein precursors between the ER and the Golgi complex.
(1) Li et al., Plant Cell (2006) in press.
