Search

The putative proteasome-associated proteins Mpa (Mycobaterium proteasomal ATPase) and PafA (proteasome accessory factor A) of the human pathogen Mycobacterium tuberculosis (Mtb) are essential for virulence and resistance to nitric oxide. However, a direct link between the proteasome protease and Mpa or PafA has never been demonstrated. Furthermore, protein degradation by bacterial proteasomes in vitro has not been accomplished, possibly due to the failure to find natural degradation substrates or other necessary proteasome co-factors. In this work, we identify the first bacterial proteasome substrates, malonyl Co-A acyl carrier protein transacylase and ketopantoate hydroxymethyltransferase, enzymes that are required for the biosynthesis of fatty acids and polyketides that are essential for the pathogenesis of Mtb. Maintenance of the physiological levels of these enzymes required Mpa and PafA in addition to proteasome protease activity. Mpa levels were also regulated in a proteasome-dependent manner. Finally, we found that a conserved tyrosine of Mpa was essential for function. Thus, these results suggest that Mpa, PafA, and the Mtb proteasome degrade bacterial proteins that are important for virulence in mice. [ABSTRACT FROM AUTHOR]

FadD28 from Mycobacterium tuberculosis belongs to the fatty-acyl AMP ligase (FAAL) family of proteins. It is essential for the biosynthesis of a virulent phthiocerol dimycocerosate (PDIM) lipid that is only found in the cell wall of pathogenic mycobacteria. The N-terminal domain, comprising of the first 460 residues, was crystallized by the hanging-drop vapour-diffusion method at 295 K. The crystals belong to space group P212121, with unit-cell parameters a = 50.97, b = 60.74, c = 136.54 Å. The crystal structure of the N-terminal domain of FadD28 at 2.35 Å resolution has been solved using the MAD method. [ABSTRACT FROM AUTHOR]

The biosynthetic machinery of polyketide synthases involves various sequential enzymatic reactions, such as initiation, elongation and cyclization, to produce polyketides. PKS18 protein from Mycobacterium tuberculosis belongs to the type III polyketide synthase family and displays an unusual starter-unit specificity to catalyze the formation of α-pyrones. This enzyme uses malonyl-CoA to iteratively extend long-chain aliphatic coenzyme A (C12 to C20) molecules, producing triketide and tetraketide pyrone products. In order to aid in understanding the structural basis of this long-chain specificity and to further characterize the enzymatic mechanism of PKS18, the protein has been crystallized. The crystal belongs to the triclinic space group P1, with unit-cell parameters a = 59.9, b = 80.7, c = 99.6 Å, α = 108.2, β = 93.0, γ = 103.7 °. [ABSTRACT FROM AUTHOR]