TASK DEFINITION: In this task, you are given an abstract of article. Your task is to generate title for this article. Preferred titles are under thirty words.
PROBLEM: The three-dimensional structure of an HNF-3/fork head DNA-recognition motif complexed with DNA has been determined by X-ray crystallography at 2.5 A resolution. This / protein binds B-DNA as a monomer, through interactions with the DNA backbone and through both direct and water-mediated major and minor groove base contacts, inducing a 13 bend. The transcription factor fold is very similar to the structure of histone H5. In its amino-terminal half, three -helices adopt a compact structure that presents the third helix to the major groove. The remainder of the protein includes a twisted, antiparallel -structure and random coil that interacts with the minor groove.

SOLUTION: Co-crystal structure of the HNF-3/fork head DNA-recognition motif resembles histone H5

PROBLEM: Urease, a nickel-dependent metalloenzyme, is synthesized by plants, some bacteria, and fungi. It catalyzes the hydrolysis of urea into ammonia and carbon dioxide. Although the amino acid sequences of plant and bacterial ureases are closely related, some biological activities differ significantly. Plant ureases but not bacterial ureases possess insecticidal properties independent of its ureolytic activity. To date, the structural information is available only for bacterial ureases although the jack bean urease (Canavalia ensiformis; JBU), the best-studied plant urease, was the first enzyme to be crystallized in 1926. To better understand the biological properties of plant ureases including the mechanism of insecticidal activity, we initiated the structural studies on some of them. Here, we report the crystal structure of JBU, the first plant urease structure, at 2.05 A resolution. The active-site architecture of JBU is similar to that of bacterial ureases containing a bi-nickel center. JBU has a bound phosphate and covalently modified residue (Cys592) by beta-mercaptoethanol at its active site, and the concomitant binding of multiple inhibitors (phosphate and beta-mercaptoethanol) is not observed so far in bacterial ureases. By correlating the structural information of JBU with the available biophysical and biochemical data on insecticidal properties of plant ureases, we hypothesize that the amphipathic beta-hairpin located in the entomotoxic peptide region of plant ureases might form a membrane insertion beta-barrel as found in beta-pore-forming toxins.

SOLUTION: Crystal structure of the first plant urease from jack bean: 83 years of journey from its first crystal to molecular structure.

PROBLEM: Bacteroidales are the most abundant Gram-negative bacteria of the human intestinal microbiota comprising more than half of the bacteria in many individuals. Some of the factors that these bacteria use to establish and maintain themselves in this ecosystem are beginning to be identified. However, ecological competition, especially interference competition where one organism directly harms another, is largely unexplored. To begin to understand the relevance of this ecological principle as it applies to these abundant gut bacteria and factors that may promote such competition, we screened Bacteroides fragilis for the production of antimicrobial molecules. We found that the production of extracellularly secreted antimicrobial molecules is widespread in this species. The first identified molecule, described in this manuscript, contains a membrane attack complex/perforin (MACPF) domain present in host immune molecules that kill bacteria and virally infected cells by pore formation, and mutations affecting key residues of this domain abrogated its activity. This antimicrobial molecule, termed BSAP-1, is secreted from the cell in outer membrane vesicles and no additional proteins are required for its secretion, processing or immunity of the producing cell. This study provides the first insight into secreted molecules that promote competitive interference among Bacteroidales strains of the human gut.

SOLUTION:
An antimicrobial protein of the gut symbiont Bacteroides fragilis with a MACPF domain of host immune proteins.