Fig. 1.

Assembly of archaeal and eubacterial proteasome core particles (CP). The CP consists of α- and β-type subunits. In T. acidophilum, the first step is the assembly of the α ring which serves as template for pro-β subunit incorporation. The dimerization of two half CP yields the pre-holo-CP which is converted into the mature CP by autocatalytic cleavage of the β-propeptides (upper panel). In R. erythropolis, the first step is the formation of an α/pro-β heterodimer. The oligomerization of seven α/pro-β dimers results in the formation of the half-CP. Two half-CP dimerize into the pre-holo-CP in which β-propeptide processing yields CP maturation (lower panel)