Ligand recognition in μ opioid receptor: experimentally based modeling of μ opioid receptor binding sites and their testing by ligand docking

For three-dimensional understanding of the mechanisms that control potency and selectivity of the ligand binding at the atomic level, we have analysed opioid receptor-ligand interaction based on the receptor's 3D model. As a first step, we have constructed molecular models for the multiple opioid receptor subtypes using bacteriorhodopsin as a template. The S-activated dihydromorphine derivatives should serve as powerful tools in mapping the three-dimensional structure of the μ opioid receptor, including the nature of the agonist-mediated conformational change that permits G protein-coupling to ‘second messenger’ effector molecules, and in identifying specific ligand-binding contacts with the μ opioid receptor. The analyses of the interactions of some opioid ligands with the predicted ligand binding sites are consistent with the results of the affinity labeling experiments.     

Synthesis of a polymide containing a glucose unit in the main chain

A new type polyamide containing a glucose unit in the main chain has been synthesized by the polymerization of C₁, C₃, C₄ blocked C₆-carboxymethylglucosamine, prepared from chitin. The deblocking procedure gave the water-soluble polyamide, of MW 1.5 × 10⁴, which can be regarded as a model for the recognition site of lectin.     

Two new components of 9 and 14 kDa from spinach photosystem I complex

Two formerly-uncharacterized subunits of 9 kDa and 14 kDa were found in spinach PSI complex. The 9 kDa subunit was released upon removal of antenna chlorophyll complex, whereas the 14 kDa subunit was tightly bound to the core complex. We determined the N-terminal amino acid sequence of the 9 kDa, and an internal sequence of the 14 kDa subunit after protease treatment, since the N-terminus of the latter protein was blocked. These partial sequences suggested that both subunits are new PSI components.     

A male infant with monosomy 21.

A male infant with total monosomy 21 identified by Q-, G- and R-banding is described. His main symptoms are hypertonia, micrognathia, microphthalmus, imperforate anus, ambiguous external genitalia, floating and malopposed thumbs, overlying fingers, right clubfoot and growth retardation. Both parents are phenotypically as well as karotypically normal.     

Electron-microscopic studies on developing intramural ganglia of the small intestine in human and rabbit fetuses.

Electron-microscopic studies were made on the appearance of synapses in the intramural ganglion (Auerbach) and findings were correlated with the onset and development of intestinal peristalsis in 6- to 30-week-old human and rabbit fetuses from the 12th day after conception until birth. At stage I, in which the small intestine shows no indication of a muscle layer or spontaneous peristalsis, primitive synapses containing several clear vesicles and a few cored vesicles are seen on neuroblasts and their processes (dendrites). At stage II, in which the circular muscle is developed and bidirectional peristalsis occurs, synaptic profiles can be classified into 3 types. Type 1 is the most numerous but seldom shows membrane specificity on the synaptic portion. Types 2 and 3 have small flattened vesicles and small round vesicles, respectively. They are further characterized by thickening of snyaptic membranes and aggregation of small clear vesicles associated with the presynaptic membrane. At stage III, the longitudinal muscle layer develops in the small intestine. At this stage, nerve terminals containing mainly cored vesicles have been observed and classified into types 4 and 5, according to their morphology. At stage IV, antiperistalsis no longer occurs and type 6 nerve terminals in the intramural ganglia can be recognized by their densely packed, large-cored vesicles. The possible physiological significance of the nerve terminals has been discussed.     

Dietary GABA induces endogenous synthesis of a novel imidazole peptide homocarnosine in mouse skeletal muscles

Amino Acids - Carnosine (β-alanyl-l-histidine) is an imidazole dipeptide present at high concentrations in skeletal muscles, where it plays a beneficial role. However, oral intake of carnosine...     

Plant stem cell research is uncovering the secrets of longevity and persistent growth

Plant stem cells have several extraordinary features: they are generated de novo during development and regeneration, maintain their pluripotency, and produce another stem cell niche in an orderly manner. This enables plants to survive for an extended period and to continuously make new organs, representing a clear difference in their developmental program from animals. To uncover regulatory principles governing plant stem cell characteristics, our research project ‘Principles of pluripotent stem cells underlying plant vitality’ was launched in 2017, supported by a Grant-in-Aid for Scientific Research on Innovative Areas from the Japanese government. Through a collaboration involving 28 research groups, we aim to identify key factors that trigger epigenetic reprogramming and global changes in gene networks, and thereby contribute to stem cell generation. Pluripotent stem cells in the shoot apical meristem are controlled by cytokinin and auxin, which also play a crucial role in terminating stem cell activity in the floral meristem; therefore, we are focusing on biosynthesis, metabolism, transport, perception, and signaling of these hormones. Besides, we are uncovering the mechanisms of asymmetric cell division and of stem cell death and replenishment under DNA stress, which will illuminate plant-specific features in preserving stemness. Our technology support groups expand single-cell omics to describe stem cell behavior in a spatiotemporal context, and provide correlative light and electron microscopic technology to enable live imaging of cell and subcellular dynamics at high spatiotemporal resolution. In this perspective, we discuss future directions of our ongoing projects and related research fields.     

Transcellobiosylation Reactions Catalyzed by Different Exoglucanase Components of a Trichoderma viride Cellulase in Aqueous Organic Solvent

The contribution of three exoglucanases from a commercial Trichoderma viride cellulase to transcellobiosylation, and the tolerance of these enzymes to acetonitrile co-solvent were studied. The enzymatic reactions were performed with p-nitrophenyl-β-d-cellobioside as the starting substrate. Among these enzymes, the least anionic exoglucanase (Exo I) showed the highest transcellobiosylation activity and acetonitrile tolerance. Exo I retained considerable activity even in 30% MeCN/water and produced p-nitrophenyl-β-d-cellotetraoside at about 1.5% conversion from the initial substrate in 30% MeCN/water. The residual activity of Exo I after incubation in MeCN/water mixture was almost identical to that of the crude cellulase and a considerable amount of the transcellobiosylation properties of the crude cellulase seemed to be attributable to this Exo I component.     

Aberrant Assembly of RNA Recognition Motif 1 Links to Pathogenic Conversion of TAR DNA-binding Protein of 43 kDa (TDP-43)

Aggregation of TAR DNA-binding protein of 43 kDa (TDP-43) is a pathological signature of amyotrophic lateral sclerosis (ALS). Although accumulating evidence suggests the involvement of RNA recognition motifs (RRMs) in TDP-43 proteinopathy, it remains unclear how native TDP-43 is converted to pathogenic forms. To elucidate the role of homeostasis of RRM1 structure in ALS pathogenesis, conformations of RRM1 under high pressure were monitored by NMR. We first found that RRM1 was prone to aggregation and had three regions showing stable chemical shifts during misfolding. Moreover, mass spectrometric analysis of aggregated RRM1 revealed that one of the regions was located on protease-resistant β-strands containing two cysteines (Cys-173 and Cys-175), indicating that this region served as a core assembly interface in RRM1 aggregation. Although a fraction of RRM1 aggregates comprised disulfide-bonded oligomers, the substitution of cysteine(s) to serine(s) (C/S) resulted in unexpected acceleration of amyloid fibrils of RRM1 and disulfide-independent aggregate formation of full-length TDP-43. Notably, TDP-43 aggregates with RRM1-C/S required the C terminus, and replicated cytopathologies of ALS, including mislocalization, impaired RNA splicing, ubiquitination, phosphorylation, and motor neuron toxicity. Furthermore, RRM1-C/S accentuated inclusions of familial ALS-linked TDP-43 mutants in the C terminus. The relevance of RRM1-C/S-induced TDP-43 aggregates in ALS pathogenesis was verified by immunolabeling of inclusions of ALS patients and cultured cells overexpressing the RRM1-C/S TDP-43 with antibody targeting misfolding-relevant regions. Our results indicate that cysteines in RRM1 crucially govern the conformation of TDP-43, and aberrant self-assembly of RRM1 at amyloidogenic regions contributes to pathogenic conversion of TDP-43 in ALS.