Acts as a regulatory subunit of the 26 proteasome which is involved in the ATP-dependent degradation of ubiquitinated proteins. Component of the 19S regulatory particle (RP/PA700) base subcomplex of the 26S proteasome. The 26S proteasome is composed of a core protease (CP), known as the 20S proteasome, capped at one or both ends by the 19S regulatory particle (RP/PA700). The RP/PA700 complex is composed of at least 17 different subunits in two subcomplexes, the base and the lid, which form the portions proximal and distal to the 20S proteolytic core, respectively. Expressed in stems, leaves, buds, flowers, siliques and developing seeds. Detected in the entire flower with strong signals in carpels, especially in differentiating ovules and the carpel wall. Patchy localization with strong levels in particular cells. In anthers, present at a high level in tetrads of microspores and the tapetum. After fertilization, mostly observed in the embryo up to the heart stage and in the chalazal endospem. Expressed at high levels in silique wall at all stages of carpel development. Ubiquitinated. Normal phenotype. Belongs to the proteasome subunit S2 family.