Dissecting the assembly pathway of the 20S proteasome

Proteasomes reach their mature active state via a complex cascade of folding, assembly and processing events, The Rhodococcus proteasome offers a means to dissect the assembly pathway and to characterize intermediates; its four subunits (alpha(1), alpha 2, beta 1, beta 2) assemble efficiently in vitro with any combination of alpha and beta. Assembly studies with wild-type and N-terminally truncated beta-subnnits in conjunction with refolding studies allowed to define the role of the propeptide,which is two-fold: It supports the initial folding of the beta-subunits and it promotes the maturation of the holoproteasomes. (C) 1997 Federation of European Biochemical Societies.