Amino acid sequence of the alpha and beta subunits of Methanosarcina barkeri ATPase deduced from cloned genes. Similarity to subunits of eukaryotic vacuolar and F0F1-ATPases

The atpA and atpB genes coding for the alpha and beta subunits, respectively, of membrane ATPase were cloned from a methanogen Methanosarcina barkeri, and the amino acid sequences of the two subunits were deduced from the nucleotide sequences. The methanogenic alpha (578 amino acid residues) and beta (459 amino acid residues) subunits were highly homologous to the large and small subunits, respectively, of vacuolar H+-ATPases; 52% of the residues of the methanogenic alpha subunit were identical with those of the large subunit of vacuolar enzyme of carrot or Neurospora crassa, respectively, and 59, 60, and 59% of the residues of the methanogenic beta subunit were identical with those of the small subunits of N. crassa, Arabidopsis thaliana, and Sacharomyces cerevisiae, respectively. The methanogenic subunits were also highly homologous to the corresponding subunits of Sulfolobus acidocaldarius ATPase. The methanogenic alpha and beta subunits showed 22 and 24% identities with the beta and the alpha subunits of Escherichia coli F1, respectively. Furthermore, important amino acid residues identified genetically in the E. coli enzyme were conserved in the methanogenic enzyme. This sequence conservation suggests that vacuolar, F1, methanogenic, and S. acidocaldarius ATPases were derived from a common ancestral enzyme.     

Urea degradation by picophytoplankton in the euphotic zone of Lake Biwa

The ability of photoautotrophic picoplankton Synechococcus to degrade urea was examined in the euphotic zone of Lake Biwa. Samples were divided into pico (0.2–2.0 μm) and larger (>2.0 μm) size fractions by filtration. The rates of urea degradation (the sum of the rates of incorporation of carbon into phytoplankton cells and of liberation of CO₂ into water) measured by radiocarbon urea were 8 and 17 μmol urea m⁻³ day⁻¹ in June and July, respectively, for the picophytoplankton in the surface water, and 196 and 96 μmol urea m⁻³ day⁻¹, respectively for the larger phytoplankton. The rates decreased with depth, somewhat similar to the vertical profiles of the photosynthetic rate. The urea degradation rates were obviously high under light conditions. In daylight, urea was degraded into two phases, carbon incorporation and CO₂ liberation, whereas in the dark it was degraded only into the CO₂ liberation phase. The contribution of picophytoplankton to total phytoplankton in urea degradation was high in the subsurface to lower euphotic layer. Urea degradation activity was higher in the picophytoplankton fraction than in the larger phytoplankton fraction. Shorter residence times of urea were obtained in the upper euphotic zone. The contribution of picophytoplankton to urea cycling was 4% to 35%. The present results suggest that the picophytoplankton Synechococcus is able to degrade urea and effectively makes use of regenerated urea as a nitrogen source in the euphotic layer, and that picophytoplankton play an important role in the biogeochemical nitrogen cycle in Lake Biwa. Received: June 25, 1998 / Accepted: February 10, 1999     

Modification of a novel angiogenic peptide, AG30, for the development of novel therapeutic agents

We previously identified a novel angiogenic peptide, AG30, with antibacterial effects that could serve as a foundation molecule for the design of wound-healing drugs. Toward clinical application, in this study we have developed a modified version of the AG30 peptide characterized by improved antibacterial and angiogenic action, thus establishing a lead compound for a feasibility study. Because AG30 has an α-helix structure with a number of hydrophobic and cationic amino acids, we designed a modified AG30 peptide by replacing several of the amino acids. The replacement of cationic amino acids (yielding a new molecule, AG30/5C), but not hydrophobic amino acids, increased both the angiogenic and the antimicrobial properties of the peptide. AG30/5C was also effective against methicillin-resistant Staphylococcus aureus (MRSA) and antibiotic-resistant Pseudomonas aeruginosa. In a diabetic mouse wound-healing model, the topical application of AG30/5C accelerated wound healing with increased angiogenesis and attenuated MRSA infection. To facilitate the eventual clinical investigation/application of these compounds, we developed a large-scale procedure for the synthesis of AG30/5C that employed the conventional solution method and met Good Manufacturing Practice guidelines. In the evaluation of stability of this peptide in saline solution, RP-HPLC analysis revealed that AG30/5C was fairly stable under 5°C for 12 months. Therefore, we propose the use of AG30/5C as a wound-healing drug with antibacterial and angiogenic actions.     

Mutant luciferase enzymes from fireflies with increased resistance to benzalkonium chloride

Benzalkonium chloride (BAC), used to extract intracellular ATP, interferes with subsequent firefly luciferase-luciferin assays. There was a significant difference among wild-type luciferases with respect to BAC resistance. Luciola lateralis luciferase (LlL) was the most tolerant, followed by Luciola cruciata luciferase (LcL) and Photinus pyralis luciferase. Random mutagenesis of thermostable mutants of LcL showed that the Glu490Lys mutation contributes to improved resistance to BAC. The corresponding Glu490Lys mutation was introduced into thermostable mutants of LlL by site-directed mutagenesis. Kinetic analysis demonstrated that the resultant LlL-217L490K mutant, having both an Ala217Leu and a Glu490Lys mutation, showed the highest resistance to BAC, with an initial remaining bioluminescence intensity of 87.4% and a decay rate per minute of 29.6% in the presence of 0.1% BAC. The Glu490Lys mutation was responsible for increased resistance to inactivation but not inhibition by BAC. The LlL-217L490K had identical thermostability and pH stability to the parental thermostable mutant. From these results, it was concluded that the LlL-217L490K enzyme is advantageous for hygiene monitoring and biomass assays based on the ATP-bioluminescence methodology. This is the first report demonstrating improved resistance to BAC of the firefly luciferase enzyme.     

Colorimetric dimethyl sulfide sensor using Rhodovulum sulfidophilum cells based on intrinsic pigment conversion by CrtA

A colorimetric whole-cell sensor for dimethyl sulfide (DMS) was constructed based on the in vivo conversion of intrinsic pigments in response to the analyte. In a marine bacterium, Rhodovulum sulfidophilum, carotenoids are synthesized via the spheroidene pathway. In this pathway, demethylspheroidene, a yellow carotenoid, is converted to spheroidene under catalysis of O-methyltransferase. Spheroidene monooxygenase (CrtA) catalyzes the terminal step of the pathway and converts spheroidene to spheroidenone, a red carotenoid. Here, the CrtA gene in R. sulfidophilum was removed and then reintroduced downstream of the DMS dehydrogenase gene promoter. Using this whole-cell sensor, 3 μM DMS or dimethyl sulfoxide can be detected without adding any color-forming reagent. The ratio of the red spheroidenone to total carotenoids increased, as the DMS concentration was raised to 0.3 mM. Comparison of the signal to the background color indicated a shift in the color coordinate from a yellow to a red hue. An intense signal was obtained with 1-day incubation at a high cell density when sensor cells at the exponential growth phase were used. These results show that the genetically engineered R. sulfidophilum cells can be used to monitor the quality of marine aquacultural environments by the naked eye.     

Mutations in the tobacco mosaic virus 30-kD protein gene overcome Tm-2 resistance in tomato.

A resistance-breaking strain of tobacco mosaic virus (TMV), Ltb1, is able to multiply in tomatoes with the Tm-2 gene, unlike its parent strain, L. Nucleotide sequence analysis of Ltb1 RNA revealed two amino acid changes in the 30-kD protein: from Cys68 to Phe and from Glu133 to Lys (from L to Ltb1). Strains with these two changes generated in vitro multiplied in tomatoes with the Tm-2 gene and induced essentially the same symptoms as those caused by Ltb1. Strains with either one of the two changes did not overcome the resistance as efficiently as Ltb1, although increased levels of multiplication were observed compared with the L strain. Results showed that both mutations are involved in the resistance-breaking property of Ltb1. Sequence analysis indicated that another resistance-breaking strain and its parent strain had two amino acid changes in the 30-kD protein: from Glu52 to Lys and from Glu133 to Lys. The fact that the amino acid changes occurred in or near the well conserved regions in the 30-kD protein suggests that the mechanism of Tm-2 resistance may be closely related to the fundamental function of the 30-kD protein, presumably in cell-to-cell movement.     

Human aquaporin adipose (AQPap) gene. Genomic structure, promoter analysis and functional mutation.

Aquaporin adipose (AQPap), which we identified from human adipose tissue, is a glycerol channel in adipocyte [Kishida et al. (2000) J. Biol. Chem. 275, 20896-20902]. In the current study, we determined the genomic structure of the human AQPap gene, and identified three AQPap-like genes that resembled (approximately 95%) AQPap, with little expression in human tissues. The AQPap promoter contained a putative peroxisome proliferator response element (PPRE) at -46 to -62, and a putative insulin response element (IRE) at -542/-536. Deletion of the PPRE abolished the pioglitazone-mediated induction of AQPap promoter activity in 3T3-L1 adipocytes. Deletion and single base pair substitution analysis of the IRE abolished the insulin-mediated suppression of the human AQPap gene. Analysis of AQPap sequence in human subjects revealed three missense mutations (R12C, V59L and G264V), and two silent mutations (A103A and G250G). The cRNA injection of the missense mutants into Xenopus oocytes revealed the absence of the activity to transport glycerol and water in the AQPap-G264V protein. In the subject homozygous for AQPap-G264V, exercise-induced increase in plasma glycerol was not observed in spite of the increased plasma noradrenaline. We suggest that AQPap is responsible for the increase of plasma glycerol during exercise in humans.     

K-ras Gene Mutation Related to Histological Atypias in Human Colorectal Adenomas

To investigate the relationship of oncogene analysis to morphology, we analyzed K-ras gene mutations by dot-blot hybridization with and without consideration of histological atypias in individual colorectal adenomas. Each of 54 colon polyps were divided into two parts after fixation. One part was used as a mass to assess point mutations; the remaining portion of each polyp was paraffin-embedded, stained with hematoxylin and eosin, and examined for point mutations related to histological atypias. In the first part of our study, K-ras gene mutations at codon 12 were detected in 13 cases (24%). In the second part of our study, 12 cases had distinctly different histological atypias. From each of these 12 cases, two areas, one with higher or one with lower grade atypia in the same polyp were excised to analyze for K-ras gene mutation. Two of these 12 cases (17%) had the mutation in different areas of the same tumor. These two cases contained the mutation only in the areas with higher grade atypia, and only one case added information regarding ras mutation upon microdissection when compared to the entire biopsy. These results suggest that oligonucleotide hybridization can identify the majority of cases containing ras mutations despite regional morphologic variation. Individual cases, however, may contain clonal subpopulations within adenomas with different ras sequences from other regions within the same adenoma.     

Non-invasive diagnosis of cutaneous leishmaniasis by the direct boil loop-mediated isothermal amplification method and MinION™ nanopore sequencing

Cutaneous leishmaniasis (CL) is gaining attention as a public health problem. We present two cases of CL imported from Syria and Venezuela in Japan. We diagnosed them as CL non-invasively by the direct boil loop-mediated isothermal amplification method and an innovative sequencing method using the MinION? sequencer. This report demonstrates that our procedure could be useful for the diagnosis of CL in both clinical and epidemiological settings.     

Effect of cholesterol on human erythrocyte membrane. A spin label study

The effect of cholesterol on the membrane fluidity of human erythrocytes has been studied by electron spin resonance (ESR) spectroscopy, sensing the motion of androstane and fatty acid spin labeles in the cell membrane and in vesicles made from extracted phospholipids. 1. Androstane spin label (ASL) was incorporated from ASL-containing phospholipid vesicles into the erythrocyte membrane, essentially by a partition mechanism in proportion to their phospholipid contents. 2. On increasing the cholesterol or ASl content in the cell membrane, the spin label was gradually immobilized. 3. ASL motion in the cell membrane seemed to be primarily determined by the cholesterol/phospholipid molar ratio, regardless of the membrane protein-lipid interaction, as judged from the temperature effects on the ESR spectra of both membranes. 4. However, glutaraldehyde pretreatment induced considerable changes of the cholesterol-lipid interaction in the cell membrane, i.e., strong immobilization and cluster formation of ASL were observed.