Training unsupported sitting in people with chronic spinal cord injuries: a randomized controlled trial.

STUDY DESIGN: Randomized, assessor-blinded trial. OBJECTIVES: To evaluate the effectiveness of a 6-week task-specific training programme on the abilities of people with chronic spinal cord injuries to sit unsupported. SETTING: NSW, Australia. METHODS: Thirty adults with spinal cord injuries of at least 1-year duration were recruited. Participants in the training group (n=15) performed up to 1 h of task-specific training three times a week for 6 weeks. Participants in the control group (n=15) did not receive any training or additional therapy. Primary outcome measures were the Canadian Occupational Performance Measure (COPM), and tests of Upper Body Sway, Maximal Balance Range and donning and doffing a T-shirt (the T-shirt test). RESULTS: The between-group mean difference (95% confidence interval) for the maximal balance range was 64 mm (95% confidence interval 20 to 108 mm; P=0.006). There were no significant between-group mean differences for the COPM and the Upper Body Sway and T-shirt tests. CONCLUSIONS: This trial shows initial support for intensive task-specific training for improving the abilities of people with chronic spinal cord injuries to sit unsupported, although the real-world implications of the observed treatment effects are yet to be determined.

High-resolution structure of a potent, cyclic proteinase inhibitor from sunflower seeds.

Proteinaceous serine proteinase inhibitors are widespread throughout the plant kingdom where they play an important role in protection against pests and pathogens. Here, we describe the isolation and characterisation of a novel 14 amino acid residue cyclic peptide from sunflower seeds, which is a potent inhibitor of trypsin (Ki=100 pM). The crystal structure of this peptide in complex with bovine beta-trypsin shows both sequence and conformational similarity with the trypsin-reactive loop of the Bowman-Birk family of serine proteinase inhibitors. This inhibitor, however, is unique in being monofunctional, cyclic and far shorter (14 amino acid residues) than inhibitors belonging to this family (typically 60-70 amino acid residues). The high potency of this peptide is likely to arise from the considerable structural rigidity achieved through its cyclic nature which is further stabilised by a single internal disulphide bond. This study helps delineate the minimal unit required for effective peptide inhibitors of serine proteinases, and will assist in the further design of inhibitors to this widespread class of enzymes.

Cubic crystals of phosphopantetheine adenylyltransferase from Escherichia coli.

Phosphopantetheine adenylyltransferase (PPAT, E.C. 2.7.7.3) catalyzes the penultimate step in coenzyme A (CoA) biosynthesis, transferring an adenylyl group from ATP to 4'-phosphopantetheine, and forming dephospho-CoA. Cubic crystals of native PPAT from Escherichia coli as well as PPAT in complex with its substrates were obtained. The crystals belong to space group I23 or I213 with unit-cell dimension a = 135.5 A. The crystals diffract to better than 1.8 A resolution on a Cu Kalpha rotating-anode generator. The asymmetric unit is likely to contain two molecules, corresponding to a packing density of 2.9 A3 Da-1.

Function from structure? The crystal structure of human phosphatidylethanolamine-binding protein suggests a role in membrane signal transduction.

BACKGROUND: Proteins belonging to the phosphatidylethanolamine-binding protein (PEBP) family are highly conserved throughout nature and have no significant sequence homology with other proteins of known structure or function. A variety of biological roles have previously been described for members of this family, including lipid binding, roles as odorant effector molecules or opioids, interaction with the cell-signalling machinery, regulation of flowering plant stem architecture, and a function as a precursor protein of a bioactive brain neuropeptide. To date, no experimentally derived structural information has been available for this protein family. In this study we have used X-ray crystallography to determine the three-dimensional structure of human PEBP (hPEBP), in an attempt to clarify the biological role of this unique protein family. RESULTS: The crystal structures of two forms of hPEBP have been determined: one in the native state (at 2.05 A resolution) and one in complex with cacodylate (at 1.75 A resolution). The crystal structures reveal that hPEBP adopts a novel protein topology, dominated by the presence of a large central beta sheet, and is expected to represent the archaetypal fold for this family of proteins. Two potential functional sites have been identified from the structure: a putative ligand-binding site and a coupled cleavage site. hPEBP forms a dimer in the crystal with a distinctive dipole moment that may orient the oligomer for membrane binding. CONCLUSIONS: The crystal structure of hPEBP suggests that the ligand-binding site could accommodate the phosphate head groups of membrane lipids, therefore allowing the protein to adhere to the inner leaf of bilipid membranes where it would be ideally positioned to relay signals from the membrane to the cytoplasm. The structure also suggests that ligand binding may lead to coordinated release of the N-terminal region of the protein to form the hippocampal neurostimulatory peptide, which is known to be active in the development of the hippocampus. These studies are consistent with a primary biological role for hPEBP as a transducer of signals from the interior membrane surface.

Engineering an intertwined form of CD2 for stability and assembly.

The amino-terminal domain of CD2 has the remarkable ability to fold in two ways: either as a monomer or as an intertwined, metastable dimer. Here we show that it is possible to differentially stabilize either fold by engineering the CD2 sequence, mimicking random mutagenesis events that could occur during molecular evolution. Crystal structures of a hinge-deletion mutant, which is stable as an intertwined dimer, reveal domain rotations that enable the protein to further assemble to a tetramer. These results demonstrate that a variety of folds can be adopted by a single polypeptide sequence, and provide guidance for the design of proteins capable of further assembly.