Structure of the Mycobacterium tuberculosis proteasome and mechanism of inhibition by a peptidyl boronate

Abstract

The substrate entrance at the end of the cylindrical proteasome appears open in the crystal structure due to partial disorder of the a -subunit N-terminal residues. However, cryo-electron microscopy of the core particle reveals a closed end, compatible with the density observed in negative-staining electron microscopy that depended on the presence of the N-terminal octapetides of the a -subunits in the companion article, suggesting that the Mtb proteasome has a gated structure. We determine for the first time the proteasomal inhibition mechanism of the dipeptidyl boronate N -(4-morpholine)carbonyl-b -(1-naphthyl)-Lalanine-L -leucine boronic acid (MLN-273), an analogue of the antimyeloma drug bortezomib. The structure improves prospects for designing Mtbspecific proteasomal inhibitors as a novel approach to chemotherapy of tuberculosis.

Characterization of the Proteasome Accessory Factor (paf) Operon inMycobacterium tuberculosis

“…4A). This result was comparable to those for previously tested interactions between other proteasome-associated components (i.e., PrcA with PrcB and Mpa with Mpa) with well-established interactions (6,7,15). Neither fusion measured ␤-galactosidase activity above background with any other proteins tested, including PafA, Mpa, and PrcA (the ␣ subunit of the M. tuberculosis proteasome) (data not shown).…”

The N-Terminal Penultimate Residue of 20S Proteasome α1 Influences its N α Acetylation and Protein Levels as Well as Growth Rate and Stress Responses of Haloferax volcanii

“…Due to partial disorder of the ␣-subunit N termini, the site of substrate entry appears open at the ends of the cylinders of archaeal and bacterial CPs (e.g., CPs of Thermoplasma acidophilum, Archaeoglobus fulgidus, and Mycobacterium tuberculosis) (13,15,27). In contrast, X-ray structures of the CPs of yeast (14) and bovine (45) do not contain this opening.…”

Self‐compartmentalized bacterial proteases and pathogenesis

“…As in eukaryotes, the bacterial 20S proteasome core particle is composed of two heptameric β -subunit rings sandwiched between heptameric rings of α -subunits ( Fig. 1B) (Tamura et al ., 1995;Hu et al ., 2006). Unlike other bacterial proteases, the bacterial proteasome catalytic subunits are similar in sequence and structure to eukaryotic proteasomes.…”

“…ClpL may serve a similar function as ClpB in Gram-positive Sousa et al ., 2000). C. Mycobacterium tuberculosis proteasome protease core (PDB ID 2FHH; Hu et al ., 2006). Each subunit is indicated in a different colour.…”