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Mycobacterium tuberculosis caseinolytic protease ClpP1 ( Mt ClpP1) is a self-compartmentalized protease consisting of two heptameric rings stacked on top of each other, thus enclosing a catalytic chamber. Within the chamber, which can be reached through two axial pores, each of the 14 identical monomers possesses a serine protease active site. The unfolding and translocation of substrates into the chamber are mediated by associated hexameric ATPases covering the axial pores. Three crystal structures of Mt ClpP1, determined by molecular replacement, are presented in this study. Two of the models were refined to a resolution of 2.6 Å and the third to 3.0 Å. It was found that disorder in the handle domain affects the formation and configuration of the tetradecamer and results in condensed structures with larger equatorial pores when compared with ClpPs from other species. Additionally, this disorder accompanies conformational changes of the residues in the catalytic triad. The models also reveal structural differences within the N-terminal hairpin-loop domain, which possibly reflect the significant differences in amino-acid sequence between Mt ClpP1 and other ClpP homologues in this region. [ABSTRACT FROM AUTHOR]

The Escherichia coli gene encoding a regulator of stringent response and virulence, DksA, which contains a canonical Zn finger motif, was cloned and expressed, and the purified protein was crystallized by the hanging-drop vapor-diffusion technique in two different space groups, P212121 (a = 91.32, b = 96.59, c = 117.48 Å) and £222 (a = 80.6, b = 115.1, c = 149.57 A). The crystals belonging to space group P212121, improved by macroseeding, diffract beyond 2.0 Å at a synchrotron. Three complete atomic resolution multiple anomalous dispersion diffraction data sets were collected from the same crystal of the P212121 crystal form at the absorption edge for Zn atoms. [ABSTRACT FROM AUTHOR]