Abstract
Two major families of seed storage proteins, 2S-albumin and prolamin, have common regions termed A, B, and C, which respectively contain highly conserved CxxL, CCxxL, and PxxC motifs. In rice endosperm, the ABC-containing α-globulin and prolamins accumulate in the protein storage vacuole (PB-II) and ER-derived protein body (PB-I), respectively. Molecular mechanisms responsible for targeting storage proteins into PB-I or PB-II are still unclear. We found that partial α-globulin polypeptide (G21-Q111), containing the A and B regions, targeted GFP into PB-I. We hypothesized the protein-protein interaction between the B region and prolamins caused the accumulation of the fusion protein in PB-I. To clarify the role of CCxxL motif in the B region for PB-I targeting, we substituted each amino acid residue in the CCxxL motif. We report the analyses of their localizations and discuss the role of the CCxxL motif in protein accumulation in PB-I.
