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1.
Structural maintenance of chromosomes (SMC) proteins play fundamental roles in higher-order chromosome dynamics from bacteria to humans. It has been proposed that the Bacillus subtilis SMC (BsSMC) homodimer is composed of two anti-parallel coiled-coil arms, each having an ATP-binding domain at its distal end. It remains totally unknown, however, how the two-armed structure supports ATP-dependent actions of BsSMC. By constructing a number of mutant derivatives including 'single-armed' BsSMC, we show here that the central hinge domain provides a structural flexibility that allows opening and closing of the two arms. This unique structure brings about bimodal regulation of the SMC ATPase cycle. Closing the arm can trigger ATP hydrolysis by allowing an end-end interaction within a dimer (intramolecular mode). When bound to DNA, ATP promotes a dimer-dimer interaction, which in turn activates their DNA-dependent ATPase activity (intermolecular mode). Our results reveal a novel mechanism of ATPase regulation and provide mechanistic insights into how eukaryotic SMC protein complexes could mediate diverse chromosomal functions, such as chromosome condensation and sister chromatid cohesion. 相似文献
2.
Studies of population dynamics, movement patterns and animal behavior usually require identification of individuals. We evaluated the reliability of using whisker spot patterns to noninvasively identify individual polar bears Ursus maritimus . We obtained the locations of polar bear whisker spots from photographs taken in western Hudson Bay, tested the independence of spot locations, estimated the complexity of each spot pattern in terms of information and determined whether each whisker spot pattern was reliable from its information content. Of the 50 whisker spot patterns analyzed, 98% contained enough information to be reliable, and this result varied little among observers. Photographs taken <50 m from polar bears were most useful. Our results suggest that individual identification of polar bears in the field based on whisker spot pattern variations is reliable. Researchers studying polar bear behavior or estimating population parameters can benefit from this method if proximity to the bears is feasible. 相似文献
3.
André B. Borle Takashi Uchikawa Julius H. Anderson 《The Journal of membrane biology》1982,68(1):37-46
Summary Stimulations or inhibitions by various agents of45Ca efflux from prelabeled cells or tissues display distinct and reproducible profile patterns when the results are plotted against time as fractional efflux ratios (FER). FER is the fractional efflux of45Ca from stimulated cells divided by the fractional efflux from a control unstimulated group. These profile patterns fall into three categories: peak patterns, exponential patterns, and mixed patterns. Each category can be positive (stimulation) or negative (inhibition). The interpretation of these profiles is difficult because45Ca efflux depends on three variables: the rate of calcium transport out of the cell, the specific activity of the cell compartment from which the calcium originates, and the concentration of free calcium in this compartment. A computer model based on data obtained by kinetic analyses of45Ca desaturation curves and consisting of two distinct intracellular pools was designed to follow the concentration of the traced substance (40Ca), the tracer (45Ca), and the specific activity of each compartment before, during, and after the stimulation or the inhibition of calcium fluxes at various pool boundaries. The computer model can reproduce all the FER profiles obtained experimentally and bring information which may be helpful to the interpretation of this type of data. Some predictions of the model were tested experimentally, and the results support the views that a peak pattern may reflect a sustained change in calcium transport across the plasma membrane, that an exponential pattern arises from calcium mobilization from an internal subcellular pool, and that a mixed pattern may be caused by a simultaneous change in calcium fluxes at both compartment boundaries. 相似文献
4.
Secondary metabolism in fungi is frequently associated with asexual and sexual development. Aspergillus parasiticus produces aflatoxins known to contaminate a variety of agricultural commodities. This strictly mitotic fungus, besides producing
conidia asexually, produces sclerotia, structures resistant to harsh conditions and for propagation. Sclerotia are considered
to be derived from the sexual structure, cleistothecia, and may represent a vestige of ascospore production. Introduction
of the aflatoxin pathway-specific regulatory gene, aflR, and aflJ, which encoded a putative co-activator, into an O-methylsterigmatocystin (OMST)-accumulating strain,A. parasiticus SRRC 2043, resulted in elevated levels of accumulation of major aflatoxin precursors, including norsolorinic acid (NOR),
averantin (AVN), versicolorin A (VERA) and OMST. The total amount of these aflatoxin precursors, NOR, VERA, AVN and OMST,
produced by the aflR plus aflJ transformants was two to three-fold that produced by the aflR transformants. This increase indicated a synergisticeffect of aflR and aflJ on the synthesis of aflatoxin precursors. Increased production of the aflatoxin precursors was associated with progressive
decrease in sclerotial size, alteration in sclerotial shape and weakening in the sclerotial structure of the transformants.
The results showed that sclerotial development and aflatoxin biosynthesis are closely related. We proposed that competition
for a common substrate, such as acetate, by the aflatoxin biosynthetic pathway could adversely affect sclerotial development
in A. parasiticus.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
5.
Adedayo O. Javadpour S. Taylor C. Anderson W.A. Moo-Young M. 《World journal of microbiology & biotechnology》2004,20(6):545-550
Bacterial cultures from a wastewater treatment plant degraded a toxic azo dye (methyl red) by decolourization. Complete decolourization
using a mixed-culture was achieved at pH 6, 30 °C within 6 h at 5 mg/l methyl red concentration, and 16 h at 20—30 mg/l. Four
bacterial species were isolated that were capable of growth on methyl red as the sole carbon source, and two were identified,
namely Vibrio logei and Pseudomonas nitroreducens. The Vibrio species showed the highest methyl red degradation activity at the optimum conditions of pH 6--7, and 30—35 °C. Analysis by
NMR showed that previously reported degradation products 2-aminobenzoic acid and N,N-dimethyl-1,4-phenylenediamine were not
observed. The decolourized dye was not toxic to a monkey kidney cell line (COS-7) at a concentration of 250 μM.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
6.
Cole ES Anderson PC Fulton RB Majerus ME Rooney MG Savage JM Chalker D Honts J Welch ME Wentland AL Zweifel E Beussman DJ 《The Journal of eukaryotic microbiology》2008,55(4):245-256
ABSTRACT. We set out to find the " fenestrin " gene, a gene whose protein is associated with numerous cellular apertures, including the nuclear exchange junction in mating Tetrahymena thermophila . First we developed protocols for imaging and isolating intact nuclear exchange junctions from conjugating cells. Proteins from these junctions were purified using SDS-PAGE, subjected to limited proteolysis, and precise molecular weights were determined by mass spectrometry. Using Protein Prospector® software and the published Tetrahymena Genome Database, genes for 15 of the most abundant proteins found in our extracts were identified. The most promising candidate was cloned by PCR, fused to yellow fluorescent protein (YFP), and placed under the control of an inducible metallothionein promoter. YFP-localization within live Tetrahymena transformants strongly suggested that one of these genes encoded the fenestrin protein, a result that was subsequently confirmed by Western blotting. 相似文献
7.
Joan Silk Jenny Short Jeffrey Roberts Jill Kusnitz 《International journal of primatology》1993,14(1):95-104
We describe some of the sources of variation in gestation length among rhesus macaques. the data were obtained from the timed-mating breeding program at the California Regional Primate Research Center (CRPRC). Information about approximately 700 pregnancies that resulted in spontaneous vaginal deliveries of liveborn young is presented. The average length of these pregnancies was 166.5 days. In this population, older females with higher parities had significantly longer pregnancies and significantly heavier infants than other females did. Other factors, including infant sex, month of conception, maternal reproductive history, and paternal identity, had no consistent effect upon gestation length. 相似文献
8.
R W Rush M J Keirse P Howat J D Baum A B Anderson A C Turnbull 《BMJ (Clinical research ed.)》1976,2(6042):965-968
A detailed retrospective analysis was made of the records of 486 preterm infants, who accounted for 5-1% of all births during 1973 and 1974. Whereas preterm delivery did not contribute to perinatal mortality in terms of stillbirth, it outweighed all other causes in terms of early neonatal deaths. Preterm birth was responsible for 85% of the early neonatal deaths not due to lethal congenital deformities. Early neonatal mortality rates were closely linked both to gestational age and birth weight and to the reason for preterm birth. Early neonatal mortality was high (97 per 1000) when preterm labour was spontaneous, whether or not associated with material or fetal disease or with multiple pregnancy, but low (27 per 1000) when preterm delivery was elective. Preventing spontaneous preterm labour would considerably reduce neonatal mortality in our community. 相似文献
9.
Comment on ‘Spectroscopie infra-rouge de quelques fractions d'acides humiques obtenues sur Sephadex’
Summary It is suggested that, in IR spectra of fractions of soil organic matter eluted from Sephadex, absorption bands ascribed to aromatic ethers, epoxide rings and alcoholic or phenolic hydroxyl groups by Bailly1 are more consistent with a conventional humic material in its carboxylate from and an associated soil clay mineral such as illite. re]19770204 相似文献
10.
Jonas Paulino de Souza Cleiton Dias do Prado Elis C.A. Eleutherio Diego Bonatto Iran Malavazi Anderson Ferreira da Cunha 《Fungal biology》2018,122(6):583-591
In Brazil, bioethanol is produced by sucrose fermentation from sugarcane by Saccharomyces cerevisiae in a fed-batch process that uses high density of yeast cells (15–25 % of wet weight/v) and high sugar concentration (18–22 % of total sugars). Several research efforts have been employed to improve the efficiency of this process through the isolation of yeasts better adapted to the Brazilian fermentation conditions. Two important wild strains named CAT-1 and PE-2 were isolated during the fermentation process and were responsible for almost 60 % of the total ethanol production in Brazil. However, in the last decade the fermentative substrate composition was much modified, since new sugar cane crops were developed, the use of molasses instead of sugar cane juice increase and with the prohibition of burning of sugarcane prior harvest. As consequence, these previously isolated strains are being replaced by new wild yeasts in most of ethanol plants. In this new scenario the isolation of novel better adapted yeasts with improved fermentative characteristics is still a big challenge. Here, we discuss the main aspects of Brazilian ethanol production and the efforts for the selection, characterization and genetic modifications of new strains with important phenotypic traits such as thermotolerance. 相似文献