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The assembly and anchorage of various pathogenic proteins on the surface of Gram-positive bacteria is mediated by the sortase family of enzymes. These cysteine transpeptidases catalyze a unique sorting signal motif located at the C-terminus of their target substrate and promote the covalent attachment of these proteins onto an amino nucleophile located on another protein or on the bacterial cell wall. Each of the six distinct classes of sortases displays a unique biological role, with sequential activation of multiple sortases often observed in many Gram-positive bacteria to decorate their peptidoglycans. Less is known about the members of the class D family of sortases (SrtD), but they have a suggested role in spore formation in an oxygen-limiting environment. Here, the crystal structure of the SrtD enzyme from Clostridium perfringens was determined at 1.99 Å resolution. Comparative analysis of the C. perfringens SrtD structure reveals the typical eight-stranded β-barrel fold observed in all other known sortases, along with the conserved catalytic triad consisting of cysteine, histidine and arginine residues. Biochemical approaches further reveal the specifics of the SrtD catalytic activity in vitro, with a significant preference for the LPQTGS sorting motif. Additionally, the catalytic activity of SrtD is most efficient at 316 K and can be further improved in the presence of magnesium cations. Since C. perfringens spores are heat-resistant and lead to foodborne illnesses, characterization of the spore-promoting sortase SrtD may lead to the development of new antimicrobial agents. [ABSTRACT FROM AUTHOR]

Although part of the coenzyme A pathway, vanin 1 (also known as pantetheinase) sits on the cell surface of many cell types as an ectoenzyme, catalyzing the breakdown of pantetheine to pantothenic acid (vitamin B5) and cysteamine, a strong reducing agent. Vanin 1 was initially discovered as a protein involved in the homing of leukocytes to the thymus. Numerous studies have shown that vanin 1 is involved in inflammation, and more recent studies have shown a key role in metabolic disease. Here, the X-ray crystal structure of human vanin 1 at 2.25 Å resolution is presented, which is the first reported structure from the vanin family, as well as a crystal structure of vanin 1 bound to a specific inhibitor. These structures illuminate how vanin 1 can mediate its biological roles by way of both enzymatic activity and protein-protein interactions. Furthermore, it sheds light on how the enzymatic activity is regulated by a novel allosteric mechanism at a domain interface. [ABSTRACT FROM AUTHOR]

The heterodimeric ligand-binding region of the Bovicola ovis ecdysone receptor has been crystallized either in the presence of an ecdysteroid or a synthetic methylene lactam insecticide. Two X-ray crystallographic structures, determined at 2.7 Å resolution, show that the ligand-binding domains of both subunits of this receptor, like those of other nuclear receptors, can display significant conformational flexibility. Thermal melt experiments show that while ponasterone A stabilizes the higher order structure of the heterodimer in solution, the methylene lactam destabilizes it. The conformations of the EcR and USP subunits observed in the structure crystallized in the presence of the methylene lactam have not been seen previously in any ecdysone receptor structure and represent a new level of conformational flexibility for these important receptors. Interestingly, the new USP conformation presents an open, unoccupied ligand-binding pocket. [ABSTRACT FROM AUTHOR]

A database application has been developed for the collection of crystallographic information. This database (the BDP) has been populated with the information found in the Protein Data Bank (PDB). The tool has been used to store crystallization data parsed out of the PDB and these data may be used to extend the crystallization information found in the Biological Macromolecule Crystallization Database (BMCD) and could be used to refine crystallization methodology. A standard is proposed for describing a crystallization experiment that will ease future crystallization data collations and analyses. [ABSTRACT FROM AUTHOR]