The sigE gene of Synechocystis sp. PCC 6803 encodes a group 2 factor for RNA polymerase and has been proposed to function in transcriptional regulation of nitrogen metabolism. By using microarray and Northern analyses, we demonstrated that the abundance of transcripts derived from genes important for glycolysis, the oxidative pentose phosphate pathway, and glycogen catabolism is reduced in a sigE mutant of Synechocystis maintained under the normal growth condition. Furthermore, the activities of the two key enzymes of the oxidative pentose phosphate pathway, glucose-6-phosphate dehydrogenase and 6-phophogluconate dehydrogenase, encoded by the zwf and gnd genes were also reduced in the sigE mutant. The dark enhancements in both enzyme activity and transcript abundance apparent in the wild type were eliminated by the mutation. In addition, the sigE mutant showed a reduced rate of glucose uptake and an increased intracellular level of glycogen. Moreover, it was unable to proliferate under the light-activated heterotrophic growth conditions. These results indicate that SigE functions in the transcriptional activation of sugar catabolic pathways in Synechocystis sp. PCC 6803.Cyanobacteria, which constitute one of the largest taxonomic groups of eubacteria, perform oxygenic photosynthesis similar to higher plants and algae. Despite the diversity in their morphology, physiology, and cellular development, all cyanobacteria are able to assimilate inorganic carbon via the reductive pentose phosphate cycle by using light energy.

We constructed and analyzed the ground surface displacement associated with the 2016 Kumamoto earthquake sequence using satellite radar interferometry images of the Advanced Land Observing Satellite 2. The radar interferogram generally shows elastic deformation caused by the main earthquakes, but many other linear discontinuities showing displacement are also found. Approximately 230 lineaments are identified, some of which coincide with the positions of known active faults, such as the main earthquake faults belonging to the Futagawa and Hinagu fault zones and other minor faults; however, there are much fewer known active faults than lineaments. In each area, the lineaments have a similar direction and displacement to each other; therefore, they can be divided into several groups based on location and major features. Since the direction of the lineaments coincides with that of known active faults or their conjugate faults, the cause of the lineaments must be related to the tectonic stress field of this region. The lineaments are classified into the following two categories: (1) main earthquake faults and their branched subfaults and (2) secondary faults that are not directly related to the main earthquake but whose slip was probably triggered by the main earthquake or aftershocks.

Murine FR-1 is a protein that is induced by fibroblast growth factor-1 and, therefore, may play a role in the regulation of the cell cycle. Sequence comparison indicates that it is a member of the NADPH-dependent aldo-keto reductase family. It bears 70% identity to human aldose reductase, an enzyme implicated in diabetic complications and a target for drug design. We have determined the 1.7 A resolution structure of the FR-1 in a ternary complex with NADPH and zopolrestat, a potent aldose reductase inhibitor. FR-1 folds into a (beta/alpha)8 barrel with an active site characterized by a preponderance of hydrophobic residues residing in a deep oblong cavity at the C-terminal end of the beta-barrel. The nicotinamide moiety of the coenzyme sits in the base of the cavity. Zopolrestat occupies the active site cavity and makes numerous contacts with several hydrophobic residues. The FR-1 ternary complex structure indicates that it uses the same general catalytic mechanism as aldose reductase and other members of the family whose structures have been determined. The protein exhibits reductase activity with DL-glyceraldehyde as a substrate and is strongly inhibited by zopolrestat. When compared with the structure of a similar ternary complex of aldose reductase, the binding site retains many of the interactions with the coenzyme and inhibitor from the conserved residues. Some differences in sequence, however, create a larger binding site that contains six more water molecules than in the aldose reductase ternary complex structure.(ABSTRACT TRUNCATED AT 250 WORDS)

The role of proline in the stability and kinetics of folding of wild-type staphylococcal nuclease and its P117G, P117T, and P31A mutants was examined as a function of guanidinium thiocyanate (Gdn-SCN) concentration. Replacement of Pro-117 with Gly or Thr caused small increases in stability, whereas substitution of Pro-31 by Ala led to a small decrease in stability. The slopes of the plots of delta G against denaturant concentration (m) for the mutant proteins are significantly smaller than for the wild-type, suggesting a decrease in the solvent-accessible surface area of the denatured state relative to that of the wild-type. The rates of unfolding and refolding were monitored using tryptophan fluorescence. The kinetic traces for refolding in the presence of Gdn-SCN were triphasic for the wild-type protein and P31A but biphasic for P117G and P117T mutants. The slower phases were typically 10% of the total amplitude except in the transition region. The rates of the fastest and medium phases of the wild-type were essentially unaffected by the mutations. Double-jump experiments in which the protein was unfolded in a high concentration of denaturant for a short time period and then refolded to final Gdn-SCN concentrations near the Cm revealed a fast increase in fluorescence emission corresponding to formation of the native state, followed by a slower decrease with an amplitude that varied with the guanidine concentration and time of unfolding.(ABSTRACT TRUNCATED AT 250 WORDS)

Asialoglycoprotein receptor (ASGP-R) is an endocytic C-type lectin receptor in hepatocytes that clears plasma glycoconjugates containing a terminal galactose or N-acetylgalactosamine. The carbohydrate recognition domain (CRD) of ASGP-R has three Ca 2+ binding sites (sites 1, 2 and 3), with Ca 2+ at site 2 being directly involved in ligand binding. Following endocytosis, the ligands are released from ASGP-R in endosomes to allow receptor recycling to the cell membrane. Although dissociation of the receptorligand complex is mediated by the acidic environment within the mature endosomes, many of these complexes also dissociate in the early time of endocytosis, where pH is approximately neutral. To investigate the mechanism of ligand release from ASGP-R in early endosomes, we examined the binding mode of Ca 2+ and ligands to ASGP-R CRD by NMR. We demonstrate that sites 1 and 2 of ASGP-R are high affinity Ca 2+ binding sites, site 3 is low affinity, and that Ca 2+ ions bind to sites 1 and 2 cooperatively. The pH and Ca 2+ concentration dependences of Ca 2+ binding states indicated that early endosome conditions favor apo-ASGP-R CRD, allowing ligand release. Our results elucidated that the cooperative binding mode of Ca 2+ makes it possible for ASGP-R to be more sensitive to Ca 2+ concentrations in early endosomes, and plays an important role in the efficient release of ligand from ASGP-R. In our proposed mechanism, ASGP-R can rapidly release Ca 2+ and its ligand even at nearly neutral pH. Sequence comparisons of endocytic C-type lectin receptors suggest that this mechanism is common in their family.