The recombinant dehydrin-like desiccation stress protein from the resurrection plant Craterostigma plantagineum displays no defined three-dimensional structure in its native state

Dehydration stress in the drought-tolerant resurrection plant Craterostigma plantagineum is accompanied by the accumulation of a large number of desiccation stress proteins (Dsp). One abundant class of these is represented by the dehydrin-related Dsp16 protein which contains 15 amino acid conserved lysine-rich repeats and a stretch of eight serine residues providing extremely hydrophilic characteristics. Recombinant Dsp16 from Craterostigma plantagineum has been cloned and expressed in Escherichia coli. The protein was purified and characterized regarding its physicochemical properties. Irrespective of successful crystallization experiments, dilute aqueous buffer solutions do not display a well-defined three-dimensional structure in terms of the canonical secondary structural elements. 1H-NMR (nuclear magnetic resonance) spectra in aqueous solution are characterized by a small chemical shift dispersion typical for an unfolded protein; however, the observed line-widths are not typical for a highly mobile random coil structure. Instead they indicate an equilibrium between conformational states with preferentially extended substructures. As a consequence of its loose structure, Dsp16 is extremely sensitive towards proteolysis unless its structure is stabilized by structure-making additives such as trifluoroethanol. Denaturants such as guanidinium chloride do not induce cooperative structural transitions. pH-dependent fluorescence changes reflect protonation/deprotonation rather than conformational changes. Sedimentation/diffusion experiments confirm the predicted molecular mass of 16 kDa. Due to the high serine/threonine content and its loose structure, Dsp16 is accessible to phosphorylation, supporting the idea that in situ the structurally relatively undefined protein may be involved in both water binding and phosphorylation.     

Cloning and expression of apolipophorin-III from the common cutworm, Spodoptera litura

Infections of the eye and genital tract with the bacterium Chlamydia trachomatis are a major cause of morbidity worldwide and are costly to treat. Development of a vaccine capable of protecting against infection or severe disease presents special challenges but would be the most effective long-term option for control of chlamydial disease. Progress has been made in understanding protective and pathological immune mechanisms in these infections, and a number of potential vaccine candidates have been developed.     

Organ injury scaling: spleen and liver (1994 revision)

A case of haemangiopericytoma of the greater omentum is reported here. We discuss the presentation, treatment and prognosis of these rare tumours.     

In vitro biotinylation provides quantitative recovery of highly purified active lactose permease in a single step

Consler et al. [Consler, T. G., Persson, B. L., et al. (1993) Proc. Natl. Acad. Sci. U.S.A. 90, 6934-6938] described a one-step purification of lactose permease, a hydrophobic membrane transport protein, from Escherichia coli. Permease constructs containing a biotin acceptor domain are biotinylated in vivo, followed by solubilization and avidin affinity purification. Although a high degree of purity is obtained, only about 15-20% of the permease is recovered due to incomplete biotinylation. In this communication, a simple modification is described that allows quantitative recovery of highly purified permease. Membranes containing permease with the biotin acceptor domain from the Klebsiella pneumoniae oxaloacetate decarboxylase are extracted with 5 M urea or treated with dicyclohexylcarbodiimide to inactivate F1/Fo ATPase and biotinylated in vitro with biotin ligase, ATP and d-biotin. Subsequently, the membranes are harvested, washed to remove free biotin and solubilized with 2% n-dodecyl-beta-D-maltopyranoside. Biotinylated permease is then purified in one step by affinity chromatography on monomeric avidin-Sepharose. The purified material is homogeneous and exhibits full activity with respect to ligand binding and counterflow.     

Isolation and sequence of the gene encoding ornithine decarboxylase, SPE1, from Candida albicans by complementation of a spe1 delta strain of Saccharomyces cerevisiae

The gene encoding ornithine decarboxylase, SPE1, from the pathogenic yeast Candida albicans has been isolated by complementation of an ornithine decarboxylase-negative (spe1 delta) strain of Saccharomyces cerevisiae. Four transformants, three of which contain plasmids with the SPE1 gene, were isolated by selection on polyamine-free medium. The C. albicans ornithine decarboxylase (ODC) showed high homology with other eukaryotic ODCs at both the amino acid and nucleic acid levels.     

How receptors talk to trimeric G proteins

Stimulated by hormones and sensory stimuli, serpentine receptors promote the release of GDP that is bound to the alpha subunit of trimeric G proteins and its replacement by GTP. Recent investigations have begun to define the sizes, shapes, and relative orientations of receptors and G proteins, the surfaces through which they interact with one another, and conformational changes in both sets of molecules that underlie receptor-catalyzed guanine-nucleotide exchange.