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71.
Parietochloris incisa comb. nov. (Trebouxiophyceae, Chlorophyta) 总被引:3,自引:0,他引:3
Shin Watanabe Seishiro Hirabayashi Sammy Boussiba Zvi Cohen Avigad Vonshak Amos Richmond 《Phycological Research》1996,44(2):107-108
A coccoid green alga, Myrmecia incisa Reisigl, was isolated from the soil of Mt Tateyama, Japan. Electronmicroscopy revealed that the organism has pyrenoids sparsely covered with starch segments and traversed by many parallel thylakoid membranes, and zoo-spores with counterclockwise basal body orientation. Due to the presence of these features, we have proposed a reclassification of M. incisa into the genus Parietochloris, Trebouxiophyceae. 相似文献
72.
73.
Summary In the production of L-cysteine from D,L-ATC stability of the relevant enzymes produced byPseudomonas sp. was tested, and strategies to improve the stability of L-ATC hydrolase were investigated in view of water activity and ionic strength. Among the three enzymes which participate in L-cysteine production, i.e., ATC racemase, L-ATC hydrolase, and S-carbamyl-L-cysteine hydrolase, L-ATC hydrolase is the least stable. Various mixtures of salts and sorbitol were added to adjust the water activities of the tested solutions. As water activity decreased from 0.93 to 0.80, the stability of L-ATC hydrolase was sharply enhanced. In the absence of sorbitol the stability of L-ATC hydrolase increased in proportion to ionic strength. Even though enzyme stability was not good at a low ionic strength, it was enhanced by lowering water activity with addition of sorbitol. The half life of L-ATC hydrolase in sorbitol-salt mixtures increased by tenfold to twentyfold compared to that of a control. 相似文献
74.
To provide further understanding of the biotransformation of benzaldehyde to L-phenylacetyl carbinol (L-PAC), an intermediate in L-ephedrine production, a kinetic model has been developed for the deactivation of pyruvate decarboxylase (PDC) by benzaldehyde. The model confirms that deactivation is first order with respect to benzaldehyde concentration and exhibits a square root dependency on time. The model covers the range of benzaldehyde concentrations 100–300 mM, as it has been shown previously that 200 mM benzaldehyde can produce L-PAC concentrations up to 190 mM (28.6 g/L) using partially purified PDC from Candida utilis. 相似文献
75.
Naoko Sakihama Izumi Nishimura Shigehiro Obata Masateru Shin 《Photosynthesis research》1995,46(1-2):323-328
When 35%-acetone extract of spinach chloroplasts was separated by SDS-PAGE, ferredoxin-NADP reductase (FNR) appeared as a single band at a molecular mass of 35 kDa. After the polypeptides on the SDS-PAGE plate were electroblotted onto PVDF membrane, the FNR band was cut out and analyzed for N-terminal structure in a gas-phase protein sequencer. Two different FNR peptides were identified: one with glutamine at its N-terminus (Gln-FNR) and the other with -pyroglutamic acid (tFNR) fraction was extracted from chloroplasts with their loosely bound FNR (lFNR) fraction removed in advance. The tFNR fraction contained Gln-FNR only. The Gln-FNR could be highly purified by affinity chromatography using a ferredoxin column. The purified Gln-FNR was digested with arginyl endopeptidase for peptide mapping and partial sequence analysis. Primary structure of Gln-FNR differed from that of lFNR
loosely bound FNR
-
tFNR
tightly bound FNR
- -pyroglutamic acid at N-terminus 相似文献
76.
Modulation of flagellar expression in Escherichia coli by acetyl phosphate and the osmoregulator OmpR. 总被引:19,自引:6,他引:13
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During the search for unknown factors involved in motility, we have found that expression of the flagellar master operon flhDC is affected by mutations of the pta and ackA genes, encoding phosphotransacetylase and acetate kinase, respectively (S. Shin, J. Sheen, and C. Park, Korean J. Microbiol. 31:504-511, 1993). Here we describe results showing that this effect is modulated by externally added acetate, except when both pta and ackA are mutated, suggesting the role of acetyl phosphate, an intermediate of acetate metabolism, as a regulatory effector. Furthermore, the following evidence indicates that the phosphorylation of OmpR, a trans factor for osmoregulation, regulates flagellar expression. First, in a strain lacking ompR, the expression of flhDC is no longer responsive to a change in the level of acetyl phosphate. Second, an increase in medium osmolarity does not decrease flhDC expression in an ompR mutant. It is known that such an increase normally enhances OmpR phosphorylation. Third, OmpR protein binds to the DNA fragment containing the flhDC promoter, and its affinity is increased with phosphorylation by acetyl phosphate. DNase I footprinting revealed the regions of the flhDC promoter protected by OmpR in the presence or absence of phosphorylation. Therefore, we propose that the phosphorylated OmpR, generated by either osmolarity change or the internal level of acetyl phosphate, negatively regulates the expression of flagella. 相似文献
77.
Peroxynitrite-Induced Cytotoxicity in PC12 Cells: Evidence for an Apoptotic Mechanism Differentially Modulated by Neurotrophic Factors 总被引:10,自引:1,他引:9
†Alvaro G. Estévez ‡Rafael Radi †Luis Barbeito §Jordan T. Shin §John A. Thompson §# Joseph S. Beckman 《Journal of neurochemistry》1995,65(4):1543-1550
Abstract: Peroxynitrite is a powerful oxidant formed by the near-diffusion-limited reaction of nitric oxide with superoxide. Large doses of peroxynitrite (>2 m M ) resulted in rapid cell swelling and necrosis of undifferentiated PC12 cells. However, brief exposure to lower concentrations of peroxynitrite (EC50 = 850 µ M ) initially (3–4 h) caused minimal damage to low-density cultures. By 8 h, cytoplasmic shrinkage with nuclear condensation and fragmentation became increasingly evident. After 24 h, 36% of peroxynitrite-treated cells demonstrated these features associated with apoptosis. In addition, 46% of peroxynitrite-treated cells demonstrated DNA fragmentation (by terminal-deoxynucleotide transferase-mediated dUTP-digoxigenin nick end-labeling) after 7 h, which was inhibited by posttreatment with the endonuclease inhibitor aurintricarboxylic acid. Serum starvation also resulted in apoptosis in control cells (23%), the percentage of which was not altered significantly by peroxynitrite treatment. Although peroxynitrite is known to be toxic to cells, the present study provides a first indication that peroxynitrite induces apoptosis. Furthermore, pretreatment of cells with nerve growth factor or insulin, but not epidermal growth factor, was protective against peroxynitrite-induced apoptosis. However, both acidic and basic fibroblast growth factors greatly increased peroxynitrite-initiated apoptosis, to 63 and 70%, respectively. Thus, specific trophic factors demonstrate differential regulation of peroxynitrite-induced apoptosis in vitro. 相似文献
78.
Akihiro Yoshida Kuniaki Takata Toshiko Kasahara Toshio Aoyagi Shozo Saito Hiroshi Hirano 《The Histochemical journal》1995,27(5):420-426
Summary Glucose is actively absorbed in the intestine by the action of the Na+-dependent glucose transporter. Using an antibody against the rabbit intestinal Na+-dependent glucose transporter (SGLT1), we examined the localization of SGLT1 immunohistochemically along the rat digestive
tract (oesophagus, stomach, duodenum, jejunum, ileum, colon and rectum). SGLT1 was detected in the small intestine (duodenum,
jejunum and ileum), but not in the oesophagus, stomach, colon or rectum. SGLT1 was localized at the brush border of the absorptive
epithelium cells in the small intestine. Electron microscopical examination showed that SGLT1 was localized at the apical
plasma membrane of the absorptive epithelial cells. SGLT1 was not detected at the basolateral plasma membrane. Along the crypt-villus
axis, all the absorptive epithelial cells in the villus were positive for SGLT1, whose amount increased from the bottom of
the villus to its tip. On the other hand, cells in the crypts exhibited little or no staining for SGLT1. Goblet cells scattered
throughout the intestinal epithelium were negative for SGLT1. These observations show that SGLT1 is specific to the apical
plasma membrane of differentiated absorptive epithelial cells in the small intestine, and suggest that active uptake of glucose
occurs mainly in the absorptive epithelial cells in the small intestine. 相似文献
79.
A single amino acid substitution within the mature sequence of ornithine aminotransferase obstructs mitochondrial entry of the precursor. 总被引:2,自引:1,他引:1
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T Kobayashi H Ogawa M Kasahara Z Shiozawa T Matsuzawa 《American journal of human genetics》1995,57(2):284-291
We describe here evidence of congenital enzyme mistargeting induced not by abnormalities in the signal sequence. We examined the molecular mechanism of hereditary ornithine aminotransferase (OAT) deficiency causing gyrate atrophy of the choroid and retina (GACR). Nucleotide sequencing of OAT cDNA generated from a GACR patient's mRNA revealed a single base change from C to G at position 268, resulting in an amino acid substitution of neutral Gln(CAA) with negatively charged Glu(GAA) at position 90 (Q90E). Immunohistochemical and transient expression analyses suggested expression of a defective labile OAT in the patient's tissues. However, high-level expression and immunocytochemical analyses elucidated that Q90E OAT (the patient's OAT) was localized within the limits of cytoplasmic free ribosomes in precursor form without any mitochondrial entry, indicating that the patient's precursor OAT was synthesized and rapidly degraded because of accumulation in the cytosol. It is interesting that, although the mutation site (Q90E) in this GACR patient's OAT was within the coding sequence of the mature protein, the precursor exhibited loss of mitochondrial targeting function. These findings suggest that not only the signal sequence but a critical part of the mature sequence plays an essential role in mitochondrial entry of the OAT precursor protein. 相似文献
80.
Tatsuo Suzutani Shin Koyano Minoru Takada Itsuro Yoshida Masanobu Azuma 《Microbiology and immunology》1995,39(10):787-794
The virulence of thymidine kinase-negative herpes simplex virus type 1 (HSV-1; VRTK? strain) and type 2 (HSV-2; UWTK? strain) was studied in comparison with that of their parental strains (VR-3 and UW-268, respectively) in an encephalitis model of adult (4-week-old) and newborn (3-day-old) mice. Viral thymidine kinase (TK) activity was essential for the maximum expression of virulence of HSV-1, because the 50% lethal dose (LD50) of VRTK? was 60 times higher than that of VR-3 in the brains of newborn mice expressing high levels of cellular TK activity. However, the UWTK? strain showed the same virulence as the parental strain in newborn mice, despite the lack virulence in adults, suggesting that replication of the UWTK? strain was completely supported by cellular TK activity. This difference in the role of viral and cellular TKs for virus growth between HSV-1 and HSV-2 was confirmed with the one-step growth of virus strains in L-M and L-M(TK?) cells. 相似文献