... 9Sregulatory particles (RP; 700 kDa). The 20S proteasomehas a cylindrical structure, consisting of a and b ringsstacked in the order of abba, and each ring contains sevenstructurally related a and ... Biological Research/Graduate School of Integrated Science, Japan, personal communication) iden-tified N-acetylation of many of the yeast 26S proteasomesubunits (a1 , a2 , a3 , a4 , a5 , a6 , a7 , a3 , a5 , ... 1475Protein assay The protein concentration of the sample was d etermined by the Bradford method [17] using c-globulin as a standard.Western blotting analysis The subunits of rice RP were separated...