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101.
Self-Protection against Cell Wall Hydrolysis in Streptococcus milleri NMSCC 061 and Analysis of the Millericin B Operon 下载免费PDF全文
Streptococcus milleri NMSCC 061 produces an endopeptidase, millericin B, which hydrolyzes the peptide moiety of susceptible cell wall peptidoglycan. The nucleotide sequence of a 4.9-kb chromosomal region showed three open reading frames (ORFs) and a putative tRNALeu sequence. The three ORFs encode a millericin B preprotein (MilB), a putative immunity protein (MilF), and a putative transporter protein (MilT). The milB gene encodes a 277-amino-acid preprotein with an 18-amino-acid signal peptide with a consensus IIGG cleavage motif. The predicted protein encoded by milT is homologous to ABC (ATP-binding cassette) transporters of several bacteriocin systems and to proteins implicated in the signal-sequence-independent export of Escherichia coli hemolysin A. These similarities strongly suggest that the milT gene product is involved in the translocation of millericin B. The gene milF encodes a protein of 302 amino acids that shows similarities to the FemA and FemB proteins of Staphylococcus aureus, which are involved in the addition of glycine to a pentapeptide peptidoglycan precursor. Comparisons of the cell wall mucopeptide of S. milleri NMSCC 061(resistant to lysis by millericin B) and S. milleri NMSCC 051(sensitive) showed a single amino acid difference. Serial growth of S. milleri NMSCC 051 in a cell wall minimal medium containing an increased concentration of leucine resulted in the in vivo substitution of leucine for threonine in the mucopeptide of the cell wall. A cell wall variant of S. milleri NMSCC 051 (sensitive) that contained an amino acid substitution (leucine for threonine) within its peptidoglycan cross bridge showed partial susceptibility to millericin B. The putative tRNALeu sequence located upstream of milB may be a cell wall-specific tRNA and could together with the milF protein, play a potential role in the addition of leucine to the pentapeptide peptidoglycan precursor and thereby, contributing to self-protection to millericin B in the producer strain. 相似文献
102.
Mervyn W. Thenabadu 《Plant and Soil》1972,36(1-3):15-29
Summary Results of a greenhouse sand-culture experiment conducted to study the effect of increasing or decreasing nitrogen supply
at various stages of growth on the growth, yield, and yield components of rice are reported.
Adequate nitrogen during the vegetative phase of growth encouraged tillering which had a bearing on the number of panicles
per plant. Excess nitrogen during the reproductive phase of growth produced panicles with unfilled or partly filled grains.
Similar effects were observed when the nitrogen status of the growth medium was changed from a low to a high level at the
stages of reduction division and anthesis.
Decrease in yield was observed when plants growing at a low level of nitrogen were transferred to a high level at the end
of the vegetative phase.
High levels of nitrogen in the growth medium at time of heading and after increased the concentration of nitrogen in the grain.
There was an inverse relationship between yield of filled grain and nitrogen in the grain. 相似文献
103.
104.
Previously, we showed that overexpression of ubiquilin reduces protein aggregates and toxicity of expanded polyglutamine proteins. Here, we investigated the mechanism of ubiquilin's protective effect. Immunofluorescence microscopy and immunoprecipitation studies indicated that ubiquilin colocalized and coimmunoprecipitated more with GFP-huntingtin-exon-1-fusion proteins containing a 74-polyglutamine tract than with GFP-huntingtin-fusion proteins containing a 28-polyglutamine tract or with GFP protein alone. Furthermore, overexpression of ubiquilin selectively enhanced the turnover of the expanded GFP-huntingtin-fusion protein. These results suggest that elevating ubiquilin levels could aid in the selective disposal of potentially toxic expanded polyglutamine proteins that are thought to cause several human diseases. 相似文献
105.
106.
Bruno Studer Torben Asp Ursula Frei Stephan Hentrup Helena Meally Aurélie Guillard Susanne Barth Hilde Muylle Isabel Roldán-Ruiz Philippe Barre Carole Koning-Boucoiran Gerda Uenk-Stunnenberg Oene Dolstra Leif Skøt Kirsten P. Skøt Lesley B. Turner Mervyn O. Humphreys Roland Kölliker Niels Roulund Klaus K. Nielsen Thomas Lübberstedt 《Molecular breeding : new strategies in plant improvement》2008,21(4):533-548
An expressed sequence tag (EST) library of the key grassland species perennial ryegrass (Lolium perenne L.) has been exploited as a resource for microsatellite marker development. Out of 955 simple sequence repeat (SSR) containing
ESTs, 744 were used for primer design. Primer amplification was tested in eight genotypes of L. perenne and L. multiflorum representing (grand-) parents of four mapping populations and resulted in 464 successfully amplified EST-SSRs. Three hundred
and six primer pairs successfully amplified products in the mapping population VrnA derived from two of the eight genotypes
included in the original screening and revealed SSR polymorphisms for 143 ESTs. Here, we report on 464 EST-derived SSR primer
sequences of perennial ryegrass established in laboratory assays, providing a dedicated tool for marker assisted breeding
and comparative mapping within and among forage and turf grasses.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
107.
The mechanism by which we age has sparked a huge number of theories, and is an area of intense debate. As the elderly population rises, the importance of elucidating these mechanisms is becoming more apparent as age is the single biggest risk factor for a number of diseases such as cancer, diabetes and neurodegenerative disease. Mitochondrial DNA (MtDNA) mutations have been shown to accumulate in cells and tissues during the ageing process; however the question as to whether these mutations have a causal role in the ageing process remains an area of uncertainty. Here we review the current literature, and discuss the evidence for and against a causal role of mtDNA mutations in ageing and in the pathogenesis of age-related disease. 相似文献
108.
Andy Hesketh Holger Kock Saraspadee Mootien Mervyn Bibb 《Molecular microbiology》2009,74(6):1427-1444
The availability of zinc was shown to have a marked influence on the biosynthesis of actinorhodin in Streptomyces coelicolor A3(2). Production of actinorhodin and undecylprodigiosin was abolished when a novel pleiotropic regulatory gene, absC, was deleted, but only when zinc concentrations were low. AbsC was shown to control expression of the gene cluster encoding production of coelibactin, an uncharacterized non‐ribosomally synthesized peptide with predicted siderophore‐like activity, and the observed defect in antibiotic production was found to result from elevated expression of this gene cluster. Promoter regions in the coelibactin cluster contain predicted binding motifs for the zinc‐responsive regulator Zur, and dual regulation of coelibactin expression by zur and absC was demonstrated using strains engineered to contain deletions in either or both of these genes. An AbsC binding site was identified in a divergent promoter region within the coelibactin biosynthetic gene cluster, adjacent to a putative Zur binding site. Repression of the coelibactin gene cluster by both AbsC and Zur appears to be required to maintain appropriate intracellular levels of zinc in S. coelicolor. 相似文献
109.
Life-history traits such as age at maturity, body size and clutch size tend to vary across a species' distribution. The purpose of our study was to describe the demography of a newly discovered population of North American wood turtles Glyptemys insculpta at the species' northern range limit, and to compare our findings to those of other studies to test hypotheses about adaptive life-history variation. Turtles were hand-captured from May to October 2005 and 2006 along a 4.5 km stretch of river located in the Sudbury District, ON, Canada (46°N). Fifty-five captured individuals provided a population density estimate of 1.3 turtles/100 m of river. Juveniles comprised 35% of wood turtles captured, and growth ring counts (i.e. age estimates) indicated recruitment in each of the past 11 years. Among populations, we found a nonlinear pattern in body size variation with the largest turtles in the north, smallest turtles in the centre of the range, and intermediate-sized turtles in the south. This nonlinear pattern in body size was reflected in clutch size variation. Selective pressures to overcome years of low recruitment may have resulted in larger body sizes and hence large clutch sizes at northern latitudes while conspecifics at southern latitudes can achieve larger body sizes because they live in a more productive environment. Population density decreased with latitude, likely as a result of a gradient in habitat productivity. 相似文献
110.
L.L. Greaves M.K. Gilbart A. Yung P. Kozlowski D.R. Wilson 《Journal of biomechanics》2009,42(3):349-354
Accurate measurement of cartilage deformation in loaded cadaver hip joints could be a valuable tool to answer clinically relevant research questions. MRI is a promising tool, but its use requires an understanding of cartilage deformation and recovery properties in the intact hip. Our objective was to answer the following questions: (1) How long does it take for hip cartilage to reach a deformed steady-state thickness distribution under simulated physiological load, and how much does the cartilage deform? (2) How long does it take for hip cartilage to return to the original cartilage thickness distribution once the load is removed?MethodsFive human hip specimens were axially loaded to 1980 N in a 7 T MR scanner and scanned every 15 min throughout loading. One specimen was scanned every hour throughout recovery from load. One repeatability specimen was loaded and scanned every day for 4 days. Hip cartilage was segmented as a single unit and thickness was measured radially.ResultsThe hip cartilage reached a steady-state thickness distribution after 225 min of load, and 16.5 h of recovery. Mean strain after 225 min of load was 30.9%. The repeatability specimen showed an average day-to-day change in mean cartilage thickness of 0.10 mm over 4 days of data collection. The amount of deformation (0.96 mm) was far greater than the image resolution (0.11 mm) and error due to repeatability (0.10 mm).ConclusionUsing an ex vivo model, this method has potential for assessing changes in hip cartilage strain due to injury or surgical intervention. 相似文献