Search

The rhizomes of Acorus tatarinowii Schott and Acorus gramineus Solander are widely used for treating amnesia in traditional Chinese medicine. In contrast, their leaves are usually discarded without their medicinal properties being known. Here, we found that the hot water extract of leaves improved cognition and tau pathology in model mice of frontotemporal dementia, similar to or even better than that of rhizomes. To explore the optimal method of processing, we made three preparations from dried leaves: hot water extract, extraction residue, and non-extracted simple crush powder. Among them, the simple crush powder had the strongest effect on tauopathy in mice. The crush powder also ameliorated Aβ and α-synuclein pathologies and restored cognition in mouse models of Alzheimer's disease and dementia with Lewy bodies. These findings suggest the potential of Acorus tatarinowii/gramineus leaves as a dietary source for dementia prevention and reveal that simple crushing is a better way to maximize their efficacy. [ABSTRACT FROM AUTHOR]

Phosphoketolase and transketolase are thiamine diphosphate‐dependent enzymes and play a central role in the primary metabolism of bifidobacteria: the bifid shunt. The enzymes both catalyze phosphorolytic cleavage of xylulose 5‐phosphate or fructose 6‐phosphate in the first reaction step, but possess different substrate specificity in the second reaction step, where phosphoketolase and transketolase utilize inorganic phosphate (Pi) and d‐ribose 5‐phosphate, respectively, as the acceptor substrate. Structures of Bifidobacterium longum phosphoketolase holoenzyme and its complex with a putative inhibitor, phosphoenolpyruvate, were determined at 2.5 Å resolution by serial femtosecond crystallography using an X‐ray free‐electron laser. In the complex structure, phosphoenolpyruvate was present at the entrance to the active‐site pocket and plugged the channel to thiamine diphosphate. The phosphate‐group position of phosphoenolpyruvate coincided well with those of xylulose 5‐phosphate and fructose 6‐phosphate in the structures of their complexes with transketolase. The most striking structural change was observed in a loop consisting of Gln546‐Asp547‐His548‐Asn549 (the QN‐loop) at the entrance to the active‐site pocket. Contrary to the conformation of the QN‐loop that partially covers the entrance to the active‐site pocket ('closed form') in the known crystal structures, including the phosphoketolase holoenzyme and its complexes with reaction intermediates, the QN‐loop in the current ambient structures showed a more compact conformation with a widened entrance to the active‐site pocket ('open form'). In the phosphoketolase reaction, the 'open form' QN‐loop may play a role in providing the binding site for xylulose 5‐phosphate or fructose 6‐phosphate in the first step, and the 'closed form' QN‐loop may help confer specificity for Pi in the second step. [ABSTRACT FROM AUTHOR]

Enzymatic amino acid assays are important in physiological research and clinical diagnostics because abnormal amino acid concentrations in biofluids are associated with various diseases. L-histidine decarboxylase from Photobacterium phosphoreum (PpHDC) is a pyridoxal 5′-phosphate-dependent enzyme and a candidate for use in an L-histidine quantitation assay. Previous cysteine substitution experiments demonstrated that the PpHDC C57S mutant displayed improved long-term storage stability and thermostability when compared with those of the wild-type enzyme. In this study, combinational mutation experiments of single cysteine substitution mutants of PpHDC were performed, revealing that the PpHDC C57S/C101V/C282V mutant possessed the highest thermostability. The stabilizing mechanism of these mutations was elucidated by solving the structures of PpHDC C57S and C57S/C101V/C282V mutants by X-ray crystallography. In the crystal structures, two symmetry-related PpHDC molecules form a domain-swapped homodimer. The side chain of S57 is solvent exposed in the structure, indicating that the C57S mutation eliminates chemical oxidation or disulfide bond formation with a free thiol group, thereby providing greater stability. Residues 101 and 282 form hydrophobic interactions with neighboring hydrophobic residues. Mutations C101V and C282V enhanced thermostability of PpHDC by filling a cavity present in the hydrophobic core (C101V) and increasing hydrophobic interactions. [ABSTRACT FROM AUTHOR]

Synthesis of 1 alpha, 25-dihydroxyvitamin D3 and its analogues by Suzuki-Miyaura that involves efficient preparation of the A-ring, a new convergent method has been developed.

G protein-coupled receptors (GPCRs) exist in equilibrium between multiple conformations, and their populations and exchange rates determine their functions. However, analyses of the conformational dynamics of GPCRs in lipid bilayers are still challenging, because methods for observations of NMR signals of large proteins expressed in a baculovirus-insect cell expression system (BVES) are limited. Here, we report a method to incorporate methyl-13C1H3-labeled alanine with > 45% efficiency in highly deuterated proteins expressed in BVES. Application of the method to the NMR observations of β2-adrenergic receptor in micelles and in nanodiscs revealed the ligand-induced conformational differences throughout the transmembrane region of the GPCR. [ABSTRACT FROM AUTHOR]

The C-terminal region of G-protein-coupled receptors (GPCRs), stimulated by agonist binding, is phosphorylated by GPCR kinases, and the phosphorylated GPCRs bind to arrestin, leading to the cellular responses. To understand the mechanism underlying the formation of the phosphorylated GPCR-arrestin complex, we performed NMR analyses of the phosphorylated β 2 -adrenoceptor (β 2 AR) and the phosphorylated β 2 AR-β-arrestin 1 complex, in the lipid bilayers of nanodisc. Here we show that the phosphorylated C-terminal region adheres to either the intracellular side of the transmembrane region or lipids, and that the phosphorylation of the C-terminal region allosterically alters the conformation around M215 5.54 and M279 6.41 , located on transemembrane helices 5 and 6, respectively. In addition, we found that the conformation induced by the phosphorylation is similar to that corresponding to the β-arrestin-bound state. The phosphorylation-induced structures revealed in this study propose a conserved structural motif of GPCRs that enables β-arrestin to recognize dozens of GPCRs.