Entamoeba histolytica is the etiological agent of amebiasis, a diarrheal disease which causes amoebic liver abscesses and amoebic colitis. Approximately 50 million people are infected worldwide with E. histolytica. With only 10% of infected people developing symptomatic amebiasis, there are still an estimated 100,000 deaths each year. Because of the emergence of resistant strains of the parasite, it is necessary to find a treatment which would be a proper response to this challenge. ADP-ribosylation factor (ARF) is a member of the ARF family of GTP-binding proteins. These proteins are ubiquitous in eukaryotic cells; they generally associate with cell membranes and regulate vesicular traffic and intracellular signalling. The crystal structure of ARF1 from E. histolytica has been determined bound to magnesium and GDP at 1.8 Å resolution. Comparison with other structures of eukaryotic ARF proteins shows a highly conserved structure and supports the interswitch toggle mechanism of communicating the conformational state to partner proteins.

The enzyme dihydrodipicolinate synthase catalyzes the committed step in the synthesis of diaminopimelate and lysine to facilitate peptidoglycan and protein synthesis. Dihydrodipicolinate synthase catalyzes the condensation of L-aspartate 4-semialdehyde and pyruvate to synthesize L-2,3-dihydrodipicolinate. Here, the cloning, expression, purification, crystallization and X-ray diffraction analysis of dihydrodipicolinate synthase from the pathogenic bacterium Bartonella henselae, the causative bacterium of cat-scratch disease, are presented. Protein crystals were grown in conditions consisting of 20%(w/v) PEG 4000, 100 mM sodium citrate tribasic pH 5.5 and were shown to diffract to ∼2.10 Å resolution. They belonged to space group P212121, with unit-cell parameters a = 79.96, b = 106.33, c = 136.25 Å. The final R values were Rr.i.m. = 0.098, Rwork = 0.183, Rfree = 0.233.

Burkholderia thailandensis is often used as a model for more virulent members of this genus of proteobacteria that are highly antibiotic-resistant and are potential agents of biological warfare that are infective by inhalation. As part of ongoing efforts to identify potential targets for the development of rational therapeutics, the structures of enzymes that are absent in humans, including that of chorismate mutase from B. thailandensis, have been determined by the Seattle Structural Genomics Center for Infectious Disease. The high-resolution structure of chorismate mutase from B. thailandensis was determined in the monoclinic space group P2 with three homodimers per asymmetric unit. The overall structure of each protomer has the prototypical AroQγ topology and shares conserved binding-cavity residues with other chorismate mutases, including those with which it has no appreciable sequence identity.