Abstract
In order to elucidate the mechanism of starch accumulation in the rice endosperm, we have been studying the function of OSK proteins in the developing seed, whose genes are transiently induced in the early developing stage. We partially purified the OSK complex from immature rice seeds and determined the molecular weight of its native form by the gel filtration chromatography. The peak of the activity was eluted around 130kDa, which is similar to yeast Snf1 or rat AMPK. Since Snf1 and AMPK consist of three subunits (α, β and γ), we have searched for interacting subunits of OSK proteins by yeast two-hybrid screening and have isolated three different β subunit homologues (β#15, β#17, β#19). While cDNA sequences of β#15 and β#17 encode the whole polypeptide of β subunit, β#19 is a shorter protein and contains only C-half (ASC domain) of the authentic β subunit.
