A respiration-dependent primary sodium extrusion system functioning at alkaline pH in the marine bacterium Vibrioalginolyticus

The membrane potential generated at pH 8.5 by K⁺-depleted and Na⁺-loaded $\text{Vibrio}\text{alginolyticus}$ is not collapsed by proton conductors which, instead, induce the accumulation of protons in equilibrium with the membrane potential. The generation of such a membrane potential and the accumulation of protons are specific to Na⁺-loaded cells at alkaline pH and are dependent on respiration. Extrusion of Na⁺ at pH 8.5 occurs in the presence of proton conductors unless respiration is inhibited while it is abolished by proton conductors at acidic pH. The uptake of α-aminoisobutyric acid, which is driven by the Na⁺-electrochemical gradient, is observed even in the presence of proton conductors at pH 8.5 but not at acidic pH. We conclude that a respiration-dependent primary electrogenic Na⁺ extrusion system is functioning at alkaline pH to generate the proton conductor-insensitive membrane potential and Na⁺ chemical gradient.     

Novel mutation that causes a structural change in a lipoprotein in the outer membrane of Escherichia coli.

A novel mutation which caused a structural change in a lipoprotein in the outer-membrane has been found in Escherichia coli K-12. The lipoprotein of the wild-type strain is known to have a peculiar amino terminal structure: glycerylcysteine with two fatty acids attached by ester linkages and one fatty acid by an amide linkage. In contrast to the wild-type lipoprotein, the mutant lipoproteins is isolated from the E. coli envelope as a dimer of molecular weight of about 15,000. The dimer can be reduced by mercaptoethanol to the lipoprotein monomer of molecular weight of about 7,500. The monomer has a free thiol group which is susceptible to monoiodacetie mutant lipoprotein is extremely low in comparison with that into the wild-type lipoprotein. These results suggest that the mutant is defective in transferring a glycerol group to the thiol group of the amino terminal cysteine residue of the lipoprotein. The gene responsible for this modification reaction has been located at 36.5 min on the E. coli chromosome.     

Two new iridoid glucosides from Ixora chinensis

From leaves and twigs of Ixora chinensis, two new iridoid glucosides, ixoroside (1) and ixoside (7,8-dehydroforsythide) (2) along with known geniposidic acid (3) have been isolated and their structures have been established.     

Clinicopathological assessment of cancer/testis antigens NY-ESO-1 and MAGE-A4 in osteosarcoma

The cancer/testis antigens (CTAs), New York esophageal squamous cell carcinoma-1 (NY-ESO-1) and melanoma antigen gene (MAGE)-A4 are normally restricted to male germ cells but are aberrantly expressed in several cancers. Considering the limited information regarding their significance in osteosarcoma (OS), the purpose of this study was to determine the clinical significance of NY-ESO-1 and MAGE-A4 expression in OS. Nine patients with OS treated at Kindai University Hospital were included in the study. The median age was 27 years, and median follow-up period was 40 months. The specimens obtained at the time of biopsy were used to perform immunostaining for NY-ESO, MAGE-A4, p53, and Ki-67. The positive cell rates and positive case rates of NY-ESO, MAGE-A4, p53, and Ki-67 were calculated. The correlation between the positive cell rate of immunohistochemical markers was also calculated. The correlation between the positive cell rate of NY-ESO-1 or MAGE-A4 and tumor size or maximum standardized uptake (SUV-max) was also determined. The positive cell rates of NY-ESO-1 or MAGE-A4 in continuous disease-free (CDF) cases were also compared with those in alive with disease (AWD) or dead of disease (DOD) cases. The average positive cell rates of NY-ESO, MAGEA4, p53, and Ki-67 were 71.7%, 85.1%, 16.2%, and 14.7%, and their positive case rates were 33.3%, 100%, 44.4%, and 100%, respectively. The positivity rates of NY-ESO-1 and p53 were strongly correlated, whereas those of NY-ESO-1 and Ki-67 were moderately correlated. The MAGE-A4 and p53 positivity rates and the MAGE-A4 and Ki-67 positive cell rates were both strongly correlated. The NY-ESO-1 and MAGE-A4 positivity rates were moderately correlated. The positive correlation between the NY-ESO-1 positive cell rate and tumor size was medium, and that between the MAGE-A4 positivity rate and SUV-max was very strong. There was no significant difference in the positive cell rates of NY-ESO-1 or MAGE-A4 between CDF cases and AWD or DOD cases. Overall, our results suggest that NY-ESO-1 and MAGE-A4 may be involved in the aggressiveness of OS.Key words: New York esophageal squamous cell carcinoma-1 (NY-ESO-1), melanoma antigen gene (MAGE)- A4, osteosarcoma, prognosis, cancer/testis antigen (CTA), immunohistochemistry     

The promoter of rbcS in a C3 plant (rice) directs organ-specific,light-dependent expression in a C4 plant (maize), but does not confer bundle sheath cell-specific expression

The small subunit of ribulose-bisphosphate carboxylase (Rubisco), encoded by rbcS, is essential for photosynthesis in both C3 and C4 plants, even though the cell specificity of rbcS expression is different between C3 and C4 plants. The C3 rbcS is specifically expressed in mesophyll cells, while the C4 rbcS is expressed in bundle sheath cells, and not mesophyll cells. Two chimeric genes were constructed consisting of the structural gene encoding -glucuronidase (GUS) controlled by the two promoters from maize (C4) and rice (C3) rbcS genes. These constructs were introduced into a C4 plant, maize. Both chimeric genes were specifically expressed in photosynthetic organs, such as leaf blade, but not in non-photosynthetic organs. The expressions of the genes were also regulated by light. However, the rice promoter drove the GUS activity mainly in mesophyll cells and relatively low in bundle sheath cells, while the maize rbcS promoter induced the activity specifically in bundle sheath cells. These results suggest that the rice promoter contains some cis-acting elements responding in an organ-pecific and light-inducible regulation manner in maize but does not contain element(s) for bundle sheath cell-specific expression, while the maize promoter does contain such element(s). Based on this result, we discuss the similarities and differences between the rice (C3) and maize (C4) rbcS promoter in terms of the evolution of the C4 photosynthetic gene.     

Localization of BAI-associated protein1/membrane-associated guanylate kinase-1 at adherens junctions in normal rat kidney cells: polarized targeting mediated by the carboxyl-terminal PDZ domains

Brain-specific angiogenesis inhibitor (BAI)-associated protein (BAP)1 (also called membrane-associated guanylate kinase [MAGI]-1) is composed of six PSD-95/Dlg-A/ZO-1 (PDZ) domains, two WW domains, and one guanylate kinase (GK) domain. We previously reported that BAP1 is localized at tight junctions in Madine Darby canine kidney (MDCK) cells and intestinal epithelial cells. Here, we have determined the localization of BAP1 in normal rat kidney (NRK) cells that do not form tight junctions. BAP1 was colocalized with E-cadherin along the lateral membrane, suggesting its localization at adherens junctions. Green fluorescent protein (GFP)-BAP1 was distributed in the cytosol in separate NRK cells, and accumulated to the cell-cell contacts when NRK cells have contact with each other. The GFP-BAP1 mutant containing either the first PDZ and GK domains or the WW and second PDZ domains was localized in the cytosol and the nucleus. The GFP-BAP1 mutant containing the second to fourth PDZ domains was distributed in the cytosol. The construct containing the fifth and sixth PDZ domains was localized at the cell-cell contacts along the lateral membrane and slightly in the nucleus, whereas the construct lacking the fifth and sixth PDZ domains was localized in the cytosol and in the nucleus. BAP1 was tyrosine-phosphorylated in vivo, but the tyrosine phosphorylation of BAP1 was not correlated with its localization. These results suggest that the signal in the carboxyl-terminal PDZ domains functions dominantly in vivo to target BAP1 to the lateral membrane, although potential nuclear localization signals exist in the N-terminal region of BAP1.