Figure 5.

Proposed model of the Mtb proteasome. The C-termini of Mpa hexamers may interact with the PrcA subunits, thereby promoting opening of the gate formed by the PrcA N-termini and allowing access into the proteolytic core. Interactions of Mpa with the protease core (β-subunit=PrcB; α-subunit=PrcA) appear to require the presence of PafA. Direct interactions between substrates, Mpa, PafA and the proteasome core have not yet been detected, possibly due to the requirement of additional factors.