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T Nogi

Publications and source records attributed to T Nogi.

14 recordsLinked to original sources
PubMed2001

Structure of the H subunit of the photosynthetic reaction center from the thermophilic purple sulfur bacterium, Thermochromatium tepidum Implications for the specific binding of the lipid molecule to the membrane protein complex.

The photosynthetic reaction center (RC) is a transmembrane protein complex that catalyzes light-driven electron transport across the photosynthetic membrane. The complete amino-acid sequence of the H subunit of the RC from a thermophilic purple sulfur bacterium, Thermochromatium tepidum, has been determined for the first time among purple sulfur bacteria. The H subunit consists of 259 amino acids and has a molecular mass of 28 187. The deduced amino-acid sequences of this H subunit showed a significant (40%) degree of identity with those from mesophilic purple nonsulfur bacteria. The determined primary structure of the H subunit was compared with the structures of mesophilic B. viridis and R. sphaeroides based on the three-dimensional structure of the H subunit from T. tepidum, which has been recently determined by X-ray crystallography. One lipid molecule was found in the crystal structure of the T. tepidum RC, and the head group of the lipid appears to be stabilized by the electrostatic interactions with the conserved basic residues in the H subunit. The above comparison has suggested the existence of a lipid-binding site on the molecular surface at which a lipid molecule can interact with the RC in a specific manner.

Amino Acid Sequence↗
PubMed2001

Position-specific and non-colinear expression of the planarian posterior (Abdominal-B-like) gene.

Hox genes are pivotal molecules in the control of morphogenesis along the anterior-posterior (AP) axis in various bilaterians. Planarians are key animals for understanding the evolution of the bilaterian body plan. Furthermore, they are also known for their strong regeneration ability and are thought to use the Hox genes in the process of reconstruction of the AP axis. In the present paper, the identification and analysis of expression of two posterior (Abdominal-B-like) genes, DjAbd-Ba and DjAbd-Bb, is reported in the planarian Dugesia japonica. DjAbd-Ba is expressed in the entire tail region and its anterior boundary is the posterior pharyngeal region. In contrast, DjAbd-Bb is expressed in several types of cells throughout the body. During regeneration, the expression of DjAbd-Ba rapidly recovers a pattern similar to that in the normal worm. These findings suggest the possibility that DjAbd-Ba is involved in the specification of the tail region. The anterior boundary of the expression domain of the posterior gene DjAbd-Ba is anterior to the domains of the central genes Plox4-Dj and Plox5-Dj. These expression patterns of planarian Hox genes seem out of the rule of spatial colinearity and may reflect an ancestral feature of bilaterian Hox genes.

Amino Acid Sequence↗
PubMed2001

Structural basis of bacterial photosynthetic reaction centers.

The photosynthetic reaction center (RC) is the first membrane protein whose three-dimensional structure was revealed at the atomic level by X-ray crystallograph more than fifteen years ago. Structural information about RC made a great contribution to the understanding of the reaction mechanism of the complicated membrane protein complex. High-resolution structures of RCs from three photosynthetic bacteria are now available, namely, those from two mesophilic purple non-sulfur bacteria, Blastochloris viridis and Rhodobacter sphaeroides, and that from a thermophilic purple sulfur bacterium, Thermochromatium tepidum. In addition, a variety of structural studies, mainly by X-ray crystallography, are still being performed to give more detailed insight into the reaction mechanism of this membrane protein. This review deals with structural studies of bacterial RC complexes, and a discussion about the electron transfer reaction between RCs and electron donors is the main focus out of several topics addressed by these structural studies. The structural data from three RCs and their electron donors provided reliable models for molecular recognition in the primary step of bacterial photosynthesis.

Bacterial Proteins↗
PubMed2000

Crystal structures of photosynthetic reaction center and high-potential iron-sulfur protein from Thermochromatium tepidum: thermostability and electron transfer.

The reaction center (RC) of photosynthetic bacteria is a membrane protein complex that promotes a light-induced charge separation during the primary process of photosynthesis. In the photosynthetic electron transfer chain, the soluble electron carrier proteins transport electrons to the RC and reduce the photo-oxidized special-pair of bacteriochlorophyll. The high-potential iron-sulfur protein (HiPIP) is known to serve as an electron donor to the RC in some species, where the c-type cytochrome subunit, the peripheral subunit of the RC, directly accepts electrons from the HiPIP. Here we report the crystal structures of the RC and the HiPIP from Thermochromatium (Tch.) tepidum, at 2.2-A and 1.5-A resolution, respectively. Tch. tepidum can grow at the highest temperature of all known purple bacteria, and the Tch. tepidum RC shows some degree of stability to high temperature. Comparison with the RCs of mesophiles, such as Blastochloris viridis, has shown that the Tch. tepidum RC possesses more Arg residues at the membrane surface, which might contribute to the stability of this membrane protein. The RC and the HiPIP both possess hydrophobic patches on their respective surfaces, and the HiPIP is expected to interact with the cytochrome subunit by hydrophobic interactions near the heme-1, the most distal heme to the special-pair.

Chromatiaceae↗
PubMed2000

Crystallization and preliminary crystallographic analysis of the high-potential iron-sulfur protein from Thermochromatium tepidum.

The high-potential iron-sulfur protein (HiPIP) is an electron carrier between the photosynthetic reaction centre and the cytochrome bc(1) complex in the electron-transfer chain of photosynthesis. The purified HiPIP from Thermochromatium tepidum (formerly Chromatium tepidum) was crystallized in a solution of 1.4 M ammonium sulfate and 0.1 M sodium citrate pH 3.5. The crystals diffract X-rays beyond 1.4 A resolution and belong to the orthorhombic space group P2(1)2(1)2(1), with unit-cell parameters a = 47.12 (6), b = 59.59 (10), c = 23.62 (3) A. The structure was preliminarily solved by the molecular-replacement method. The crystal structure of HiPIP from T. tepidum showed that the proteins exist as monomers, although HiPIPs from several other species can form dimers.

Bacterial Proteins↗
PubMed1999

The relationship between ocular melatonin and dopamine rhythms in the pigeon: effects of melatonin inhibition on dopamine release.

Our previous study has shown that the phases of circadian rhythms of ocular melatonin and dopamine are always opposite and intraocular melatonin injection suppresses dopamine release. Therefore, it is possible that dopamine rhythms result from inhibitory action of melatonin. We have examined this possibility in the following experiments. In the first experiment effects of continuous light on melatonin and dopamine release were examined. The data indicated that continuous light exposure resulted in loss of circadian rhythmicity of melatonin and dopamine by suppressing melatonin and enhancing dopamine levels throughout the day. To further examine the effects of light in the second experiment, 2 h light pulse was applied during the night, then temporal changes of melatonin and dopamine release were studied. The light pulse rapidly suppressed melatonin release, whereas it rapidly increased dopamine release. These changes occurred within 30 min in both melatonin and dopamine. However, the recovery after the cessation of the light stimulus was slower in melatonin than dopamine. In the third experiment it was tested if dopamine release was increased by lowering melatonin release with an intraocular injection of the D2 agonist, quinpirol. Although quinpirol strongly inhibited melatonin release independently of the time of injection, dopamine did not always increase by the inhibition of melatonin. These results indicate that ocular dopamine rhythms are not simply produced by melatonin inhibitory action.

Animals↗
PubMed1999

Purification, crystallization, and preliminary X-ray crystallographic analysis of thermus thermophilus V(1)-ATPase B subunit.

The gene of V(1)-ATPase B subunit from the thermophilic eubacterium Thermus thermophilus has been cloned and the protein overproduced in Escherichia coli. The purified protein, with a molecular weight of 53.2 kDa, was crystallized from 10% (w/v) polyethylene glycol 1000, 120 mM magnesium chloride, and 100 mM Na-tricine, pH 8.0, by the vapor diffusion method. The crystals diffracted X-rays beyond 3.5 A on a synchrotron radiation source. The crystals belong to the monoclinic space group C2, with unit cell dimensions of a = 153.1 A, b = 129.6 A, c = 92.7 A, and beta = 100.3 degrees. Assuming that three or four molecules are contained in an asymmetric unit, the V(M) value is calculated as 2.8 or 2.1 A (3)/Da, respectively.

Crystallization↗
PubMed1999

Ectopic pharynxes arise by regional reorganization after anterior/posterior chimera in planarians.

To elucidate the mechanisms underlying pharynx regeneration in planarians, we transplanted pieces excised from various regions of the body into the prepharyngeal or postpharyngeal region, since it has been shown that such transplantation experiments can induce ectopic pharynx formation. We confirmed the ectopic formation of pharynxes by expression of the myosin heavy chain gene specific to pharynx muscles (DjMHC-A). To investigate the cellular events after grafting, we also stained such transplanted worms by in situ hybridization using neuronal cell- and mucous producing cell-type-specific marker genes which can detect formation of brain and prepharyngeal region, respectively. When the head piece was transplanted into the tail region, ectopic formation of the head, prepharyngeal and pharynx region was observed in the postpharyngeal region anterior to the graft, while these organs were formed in the reversed polarity along the anterior-posterior (A-P) axis. Furthermore, in the tail region posterior to the graft, ectopic formation of the prepharyngeal and pharynx region was observed. In the reverse combination, when a tail piece was transplanted into the prepharyngeal region, ectopic formation of prepharyngeal and pharynx region was observed in the region between the head and the graft, and an additional ectopic pharynx was also formed in reverse polarity in the region between the graft and host pharynx. These results clearly indicated that ectopic pharynxes were formed as a consequence of the regional reorganization induced by interaction between the host and graft. Furthermore, chimeric analyses demonstrated that the cells participating in ectopic pharynx formation were not exclusively derived from the host or donor cells in the worm, suggesting that the stem cells of the host and donor may change their differentiation pattern due to altered regionality. To further investigate if regional reorganization is induced after grafting, expression of a Hox gene was analyzed in the transplanted worms by whole-mount in situ hybridization. The expression of the Hox gene along the A-P axis was apparently rearranged after grafting of the head piece into the tail region. These results suggest that grafting of the head piece may rearrange the regionality of the host tail, and that stem cells in the region newly defined as pharynx-forming may start to regenerate a pharynx.

Animals↗
PubMed1998

Phase-relationship and mutual effects between circadian rhythms of ocular melatonin and dopamine in the pigeon.

In order to study the mechanisms of ocular circadian rhythms in the pigeon, we measured melatonin and dopamine simultaneously from the eye using in vivo microdialysis. In experiment 1, the phase relationship between circadian rhythms of ocular melatonin and dopamine under light-dark cycles (LD) and continuous dim light (LLdim) was examined. Under LD, melatonin was high during the dark and low during the light. On the other hand dopamine was high during the light and low during the dark. These rhythms with the anti-phase relationship were maintained after the birds were transferred from LD to LLdim. In experiment 2, effects of a single light pulse on melatonin and dopamine rhythms were examined. A light pulse at CT18 rapidly suppressed melatonin release to the daytime level, whereas it rapidly increased dopamine release to the daytime level. The light pulse also affected the phases of melatonin and dopamine rhythms, inducing phase advances of both rhythm without changing the anti-phase relationship before the light pulse. In experiment 3, effects of an intraocular injection of dopamine or melatonin on their circadian rhythms were examined. A dopamine injection during the subjective night suppressed melatonin release and induced a light-pulse type phase shift in both melatonin and dopamine rhythms. On the other hand, a melatonin injection during the subjective day suppressed dopamine release and induced a dark-pulse type phase shift. These results are compatible with either one or two oscillator models, but the interaction between melatonin and dopamine is, in either case considered as an important mechanism regulating ocular circadian rhythms of the pigeon.

Animals↗
PubMedDate not supplied

In vivo microdialysis studies of pineal and ocular melatonin rhythms in birds.

Pineal and retinal melatonin has an important role in the control of avian circadian rhythms. In order to study the mechanisms of circadian rhythms of melatonin synthesis in the pineal and in the eye, in vivo microdialysis was applied to these organs. In both pigeons and Japanese quails, pineal and ocular melatonin levels were high during the dark and low during the day under light-dark (LD) cycles. These rhythms persisted under constant dim light (LLdim) conditions indicating the circadian nature of pineal and ocular melatonin release. Light has two effects on melatonin synthesis. One is acute inhibition of melatonin synthesis and the other is entrainment of circadian melatonin rhythms. We have examined photoreceptors mediating these effects in the pigeon. The results have indicated that the eyes are not involved in light-induced suppression and photic entrainment of pineal melatonin release, and pineal photoreceptors themselves are likely to mediate these effects. Concerning ocular melatonin, retinal photoreceptors seem to mediate light-induced suppression and photic entrainment and no evidence supporting mediation of extraretinal photoreceptors was obtained. Because dopamine is implicated in retinal melatonin synthesis, we measured dopamine and melatonin release simultaneously from the eye of pigeon. In contrast to melatonin rhythms, dopamine increased during the day and decreased during the dark. This antiphase relationship between melatonin and dopamine persisted in LLdim, suggesting an interaction between these two rhythms. The results of an intraocular injection of dopamine or melatonin in the phase of melatonin and dopamine rhythms indicated that the interaction is required for maintaining the antiphase relationship between the two rhythms.

Animals↗