The structure of Yersinia pestis V-antigen, an essential virulence factor and mediator of immunity against plague.

The LcrV protein (V-antigen) is a multifunctional virulence factor in Yersinia pestis, the causative agent of plague. LcrV regulates the translocation of cytotoxic effector proteins from the bacterium into the cytosol of mammalian cells via a type III secretion system, possesses antihost activities of its own, and is also an active and passive mediator of resistance to disease. Although a crystal structure of this protein has been actively sought for better understanding of its role in pathogenesis, the wild-type LcrV was found to be recalcitrant to crystallization.

Similar modes of polypeptide recognition by export chaperones in flagellar biosynthesis and type III secretion.

Assembly of the bacterial flagellum and type III secretion in pathogenic bacteria require cytosolic export chaperones that interact with mobile components to facilitate their secretion. Although their amino acid sequences are not conserved, the structures of several type III secretion chaperones revealed striking similarities between their folds and modes of substrate recognition. Here, we report the first crystallographic structure of a flagellar export chaperone, Aquifex aeolicus FliS.

Differential effects of supplementary affinity tags on the solubility of MBP fusion proteins.

It is difficult to imagine any strategy for high-throughput protein expression and purification that does not involve genetically engineered affinity tags. Because of its ability to enhance the solubility and promote the proper folding of its fusion partners, Escherichia coli maltose-binding protein (MBP) is a particularly useful affinity tag. However, not all MBP fusion proteins bind efficiently to amylose resin, and even when they do it is usually not possible to obtain a sample of adequate purity after a single affinity step.

Characterization of four orthologs of stringent starvation protein A.

Orthologous proteins can be beneficial for X-ray crystallographic studies when a protein from an organism of choice fails to crystallize or the crystals are not suitable for structure determination. Their amino-acid sequences should be similar enough that they will share the same fold, but different enough so that they may crystallize under alternative conditions and diffract to higher resolution. This multi-species approach was employed to obtain diffraction-quality crystals of the RNA polymerase (RNAP) associated stringent starvation protein A (SspA).

Maltodextrin-binding proteins from diverse bacteria and archaea are potent solubility enhancers.

Escherichia coli maltose-binding protein (MBP) is frequently used as an affinity tag to facilitate the purification of recombinant proteins. An important additional attribute of MBP is its remarkable ability to enhance the solubility of its fusion partners. MBPs are present in a wide variety of microorganisms including both mesophilic and thermophilic bacteria and archaea.