Showing papers by "Michio Murata published in 2017"
TL;DR: It is suggested that SM continually and rapidly exchanges between CD59-associated raft domains and the bulk PM, in cholesterol- and sphingosine backbone–dependent manners.
Abstract: Sphingomyelin (SM) has been proposed to form cholesterol-dependent raft domains and sphingolipid domains in the plasma membrane (PM). How SM contributes to the formation and function of these domains remains unknown, primarily because of the scarcity of suitable fluorescent SM analogs. We developed new fluorescent SM analogs by conjugating a hydrophilic fluorophore to the SM choline headgroup without eliminating its positive charge, via a hydrophilic nonaethylene glycol linker. The new analogs behaved similarly to the native SM in terms of their partitioning behaviors in artificial liquid order-disorder phase-separated membranes and detergent-resistant PM preparations. Single fluorescent molecule tracking in the live-cell PM revealed that they indirectly interact with each other in cholesterol- and sphingosine backbone–dependent manners, and that, for ∼10–50 ms, they undergo transient colocalization-codiffusion with a glycosylphosphatidylinositol (GPI)-anchored protein, CD59 (in monomers, transient-dimer rafts, and clusters), in CD59-oligomer size–, cholesterol-, and GPI anchoring–dependent manners. These results suggest that SM continually and rapidly exchanges between CD59-associated raft domains and the bulk PM.
105 citations
TL;DR: Two new homologues, amphidinols 20 (AM20, 1) and 21 (AM21, 2), were isolated from Amphidinium carterae collected in Korea and their structures were elucidated by detailed NMR analyses as amphid inol 6-type compounds with remarkably long polyol chains.
Abstract: Amphidinols are polyketide metabolites produced by marine dinoflagellates and are chiefly composed of a long linear chain with polyol groups and polyolefins. Two new homologues, amphidinols 20 (AM20, 1) and 21 (AM21, 2), were isolated from Amphidinium carterae collected in Korea. Their structures were elucidated by detailed NMR analyses as amphidinol 6-type compounds with remarkably long polyol chains. Amphidinol 21 (2) has the longest linear structure among the amphidinol homologues reported so far. The congeners, particularly amphidinol 21 (2), showed weaker activity in hemolysis and antifungal assays compared to known amphidinols.
24 citations
TL;DR: A nanosecond pump–probe device for time-resolved serial femtosecond crystallography has been developed at SACLA.
Abstract: X-ray free-electron lasers (XFELs) have opened new opportunities for time-resolved X-ray crystallography. Here a nanosecond optical-pump XFEL-probe device developed for time-resolved serial femtosecond crystallography (TR-SFX) studies of photo-induced reactions in proteins at the SPring-8 Angstrom Compact free-electron LAser (SACLA) is reported. The optical-fiber-based system is a good choice for a quick setup in a limited beam time and allows pump illumination from two directions to achieve high excitation efficiency of protein microcrystals. Two types of injectors are used: one for extruding highly viscous samples such as lipidic cubic phase (LCP) and the other for pulsed liquid droplets. Under standard sample flow conditions from the viscous-sample injector, delay times from nanoseconds to tens of milliseconds are accessible, typical time scales required to study large protein conformational changes. A first demonstration of a TR-SFX experiment on bacteriorhodopsin in bicelle using a setup with a droplet-type injector is also presented.
22 citations
TL;DR: It is concluded that the long-chain base length of ceramide is more important than the acyl chain length in determining the lateral segregation of the ceramide-rich gel phase and intermolecular interactions therein.
22 citations
TL;DR: The results suggest that OSW-1/cholesterol interaction is likely to cause membrane permeabilization and pore formation without destroying the whole membrane integrity, which could partly be responsible for its highly potent cell toxicity.
18 citations
TL;DR: The stable C-N axial chirality in a 1-phenyl-6-aminouracil scaffold owing to the presence of various functional groups at the ortho-position of the N(1)-phenyl group is reported, demonstrating the potential utility of stableC-N bond atropisomers in the development of chiral drugs.
17 citations
TL;DR: In the gel phase, sterol effects on the PCer-rich gel phase were markedly influenced by the acyl chain composition of the fluid PC, and the same was true for fluid-phase interactions involving the sterols.
12 citations
TL;DR: The results demonstrate that inter-lipid FRET intensity was significantly higher in the Lo domain than in the Ld domain, resulting in a clear and distinguishable contrast between the two domains even in poorly phase-separated giant unilamellar vesicles.
Abstract: Imaging the distribution of sphingomyelin (SM) in membranes is an important issue in lipid-raft research. Recently we developed novel fluorescent SM analogs that exhibit partition and dynamic behaviors similar to native SM, and succeeded in visualizing lateral domain-segregation between SM-rich liquid-ordered (Lo) and SM-poor liquid-disordered (Ld) domains. However, because the fluorescent contrast between these two domains depends directly on their partition ratio for the fluorescent SMs, domain-separation becomes indeterminate when the distribution difference is not great enough. In this study, we propose the use of inter-lipid Forster resonance energy transfer (FRET) imaging between fluorescent SMs to enhance the contrast of the two domains in cases in which the inter-domain difference in SM distribution is inadequate for conventional monochromic imaging. Our results demonstrate that inter-lipid FRET intensity was significantly higher in the Lo domain than in the Ld domain, resulting in a clear and distinguishable contrast between the two domains even in poorly phase-separated giant unilamellar vesicles. In addition, we show that inter-lipid FRET imaging is useful for selective visualization of highly condensed assemblies and/or clusters of SM molecules in living cell membranes. Thus, the inter-lipid FRET imaging technique can selectively emphasize the SM-condensed domains in both artificial and biological membranes.
10 citations
TL;DR: Structure-activity relationship studies of maitotoxin (MTX), a marine natural product produced by an epiphytic dinoflagellate, were conducted using chemically synthesized model compounds corresponding to the partial structures of MTX using the LMNO ring system and the NOPQR(S) ring system.
Abstract: Structure–activity relationship studies of maitotoxin (MTX), a marine natural product produced by an epiphytic dinoflagellate, were conducted using chemically synthesized model compounds corresponding to the partial structures of MTX. Both enantiomers of the LMNO ring system were synthesized via aldol reaction of the LM ring aldehyde and the NO ring ketone. These fragments were derived from a common cis-fused pyranopyran intermediate prepared through a sequence involving Nozaki–Hiyama–Kishi reaction, intramolecular oxa-Michael addition, and Pummerer rearrangement. The NOPQR(S) ring system, in which the original seven-membered S ring was substituted with a six-membered ring, was also synthesized through the coupling of the QR(S) ring alkyne and the NO ring aldehyde and the construction of the P ring via 1,4-reduction, dehydration, and hydroboration. The inhibitory activities of the synthetic specimens against MTX-induced Ca2+ influx were evaluated. The LMNO ring system and its enantiomer induced 36 and 18%...
9 citations
TL;DR: A functionalized bicyclic lactam that was used as a key intermediate in an efficient synthesis of the pharmacophore of potent marine toxin spirolide C was synthesized by using a highly selective Diels–Alder reaction.
8 citations
Patent•
05 Oct 2017
TL;DR: In this paper, a heavy atom compound was proposed to perform the determination of a phase of a crystal of a membrane protein easily without deteriorating the quality of the crystal and also makes it possible to analyze the structures of various membrane proteins.
Abstract: Disclosed are: a heavy atom compound which makes it possible to perform the determination of a phase of a crystal of a membrane protein easily without deteriorating the quality of the crystal and also makes it possible to analyze the structures of various membrane proteins; a composition for promoting the crystallization of a membrane protein; and a method for analyzing the structure of a membrane protein using the composition. The heavy atom compound according to the present invention is a compound represented by formula (I) (wherein X1 represents a single bond, an oxygen atom or -NR1-; Z represents an aryl group in which at least one hydrogen atom is substituted by a halogen atom, or the like; and A represents an alkyl group which has 5 to 20 carbon atoms and may form a branch or a ring, or the like).