Structural Basis of Mitochondrial Scaffolds by Prohibitin Complexes : Insight into a Role of the Coiled-Coil Region

The coiled-coil motif mediates subunit oligomerization and scaffolding and underlies several fundamental biologic processes. Prohibitins (PHBs), mitochondrial inner membrane proteins involved in mitochondrial homeostasis and signal transduction, are predicted to have a coiled-coil motif, but their structural features are poorly understood. Here we solved the crystal structure of the heptad repeat (HR) region of PHB2 at 1.7-Å resolution, showing that it assembles into a dimeric, antiparallel coiled-coil with a unique negatively charged area essential for the PHB interactome in mitochondria. Disruption of the HR coiled-coil abolishes well-ordered PHB complexes and the mitochondrial tubular networks accompanying PHB-dependent signaling. Using a proximity-dependent biotin identification (BioID) technique in live cells, we mapped a number of mitochondrial intermembrane space proteins whose association with PHB2 relies on the HR coiled-coil region. Elucidation of the PHB complex structure in mitochondria provides insight into essential PHB interactomes required for mitochondrial dynamics as well as signal transduction

Correlation between thermal aggregation and stability of lysozyme with salts described by molar surface tension increment: an exceptional propensity of ammonium salts as aggregation suppressor

Protein aggregation is a critical problem for biotechnology and pharmaceutical industries.Despite the fact that soluble proteins have been used for many applications, our understandingof the effect of the solution chemistry on protein aggregation still remains to be elucidated.This paper investigates the process of thermal aggregation of lysozyme in the presence ofvarious types of salts. The simple law was found; the aggregation rate of lysozyme increasedwith increasing melting temperature of the protein (Tm) governed by chemical characteristicsof additional salts. Ammonium salts were, however, ruled out; the aggregation rates oflysozyme in the presence of the ammonium salts were smaller than the ones estimatedfrom Tm. Comparing with sodium salts, ammonium salts increased the solubility of thehydrophobic amino acids, indicating that ammonium salts adsorb the hydrophobic region ofproteins, which leads to the decrease in aggregation more effectively than sodium salts. Thepositive relation between aggregation rate and Tm was described by another factor such as thesurface tension of salt solutions. Fourier transform infrared spectral analysis showed thatthe thermal aggregates were likely to form b-sheet in solutions that give high molar surfacetension increment. These results suggest that protein aggregation is attributed to the surfacefree energy of the solution

Laparoscopic Resection of a Jejunal Mesenteric Pseudocyst

An unusual case of a jejunal mesenteric pseudocyst treated by laparoscopic resection is reported. A 44-year-old woman was admitted to our hospital with intermittent upper abdominal pain and diarrhea. Physical examination revealed slight periumbilical tenderness, and no masses were palpable. Contrast-enhanced computed tomography showed a 4-cm-sized nonenhancing high-density mass with a heterogeneous pattern on a proximal small bowel loop. Based on these findings, a gastrointestinal stromal tumor accompanied by hemorrhagic and cystic change, a mesenteric hematoma, or a desmoid tumor was diagnosed. Laparoscopy was performed to obtain an accurate diagnosis. Exploration of the abdominal cavity identified a 4-cm mass originating from the mesentery of the jejunum. Segmental resection of the jejunum and its mesentery, including the mass, was performed. Macroscopically, the mass appeared to be a cystic mass of the jejunal mesentery. The mass within the cyst lumen consisted of white clayish material with no specific pathology. The final pathological diagnosis was a mesenteric pseudocyst. The patient had an uneventful postoperative course

Switchable quaternary ammonium transformation leading to salinity-tolerance-conferring plant biostimulants

Since their discovery by Menshutkin in 1890, quaternary ammonium salts have been synthesized by alkylating tertiary amines, with the development of new synthetic methods having received limited attention. Here we describe a photoredox-catalyzed method for synthesizing quaternary ammonium salts that involves reacting α-haloalkylammonium salts with olefins. This chemistry enables selective and switchable alkylations and alkenylations that afford a variety of structurally new quaternary ammonium salts. The key to success is attributable to the photocatalytic generation of distonic α-ammonium radicals under both oxidative and reductive quenching conditions. Furthermore, during the course of our reaction-development-based chemical-screening campaign, we serendipitously discovered that the synthesized quaternary ammonium salts confer plants with salinity tolerance. The discovery of a novel class of salinity-tolerance-conferring molecule is expected to impact agrochemical development as salinity damage increasingly becomes a global problem