排序方式: 共有38条查询结果,搜索用时 31 毫秒
1.
In bacteria, membrane transporters of the cation diffusion facilitator (CDF) family participate in Zn2 +, Fe2 +, Mn2 +, Co2 + and Ni2 + homeostasis. The functional role during infection processes for several members has been shown to be linked to the specificity of transport. Sinorhizobium meliloti has two homologous CDF genes with unknown transport specificity. Here we evaluate the role played by the CDF SMc02724 (SmYiiP). The deletion mutant strain of SmYiiP (ΔsmyiiP) showed reduced in vitro growth fitness only in the presence of Mn2 +. Incubation of ΔsmyiiP and WT cells with sub-lethal Mn2 + concentrations resulted in a 2-fold increase of the metal only in the mutant strain. Normal levels of resistance to Mn2 + were attained by complementation with the gene SMc02724 under regulation of its endogenous promoter. In vitro, liposomes with incorporated heterologously expressed pure protein accumulated several transition metals. However, only the transport rate of Mn2 + was increased by imposing a transmembrane H+ gradient. Nodulation assays in alfalfa plants showed that the strain ΔsmyiiP induced a lower number of nodules than in plants infected with the WT strain. Our results indicate that Mn2 + homeostasis in S. meliloti is required for full infection capacity, or nodule function, and that the specificity of transport in vivo of SmYiiP is narrowed down to Mn2 + by a mechanism involving the proton motive force. 相似文献
2.
Several methods for determining the diversity of Lactobacillus spp were evaluated with the purpose of developing a realistic approach for further studies. The patient population was comprised of young children with an oral disease called severe early childhood caries. The ultimate goal of these studies was to ascertain the role of lactobacilli in the caries process. To accomplish that goal, we evaluated several methods and approaches for determining diversity including AP-PCR, chromosomal DNA fingerprinting, denaturing gradient gel electrophoresis, and 16S rRNA gene sequencing. Central to these methods was the gathering and screening of isolates from cultivation medium. Using various estimates of diversity, we addressed the question as to how many isolates represent the overall diversity and how cultivation compares to non-cultivation techniques. Finally, we proposed a working approach for achieving the goals outlined framed by both practical constraints in terms of time, effort and efficacy while yielding a reliable outcome. 相似文献
3.
Song YH Choi E Park SH Lee SH Cho H Ho WK Ryu SY 《Free radical biology & medicine》2011,51(9):1708-1716
Oxidative stress remodels Ca2+ signaling in cardiomyocytes, which promotes altered heart function in various heart diseases. Ca2+/calmodulin-dependent protein kinase II (CaMKII) was shown to be activated by oxidation, but whether and how CaMKII links oxidative stress to pathophysiological long-term changes in Ca2+ signaling remain unknown. Here, we present evidence demonstrating the role of CaMKII in transient oxidative stress-induced long-term facilitation (LTF) of L-type Ca2+ current (ICa,L) in rat cardiomyocytes. A 5-min exposure of 1 mM H2O2 induced an increase in ICa,L, and this increase was sustained for ~ 1 h. The CaMKII inhibitor KN-93 fully reversed H2O2-induced LTF of ICa,L, indicating that sustained CaMKII activity underlies this oxidative stress-induced memory. Simultaneous inhibition of oxidation and autophosphorylation of CaMKII prevented the maintenance of LTF, suggesting that both mechanisms contribute to sustained CaMKII activity. We further found that sarcoplasmic reticulum Ca2+ release and mitochondrial ROS generation have critical roles in sustaining CaMKII activity via autophosphorylation- and oxidation-dependent mechanisms. Finally, we show that long-term remodeling of the cardiac action potential is induced by H2O2 via CaMKII. In conclusion, CaMKII and mitochondria confer oxidative stress-induced pathological cellular memory that leads to cardiac arrhythmia. 相似文献
4.
Karachi is one of the most populated urban agglomerations in the world. No categorical study has yet discussed the geochemical baseline concentrations of metals in the urban soil of Karachi. The main objectives of this study were to establish geochemical baseline values and to assess the pollution status of different heavy metals. Geochemical baseline concentrations of heavy metals were estimated using the cumulative frequency distribution (CDF) curves. The estimated baseline concentrations of Pb, Cr, Cu, Zn and Fe were 56.23, 12.9, 36.31, 123.03 and 11,776 mg kg−1, respectively. The pollution status of heavy metals in urban soils was evaluated using different quantitative indices (enrichment factor–EF, Geo-accumulation Index–Igeo, and pollution index–PI). Enrichments factors of the selected heavy metals determined by using Fe as a normalizer showed that metal contamination was the product of anthropogenic activities. The urban soils of Karachi were found to have a moderate to moderately severe enrichment with Pb, whereas Cr and Cu has moderate and Zn has minor enrichment. Igeo results indicated moderate soil contamination by Pb at some of the sampling locations. PI for Pb, Cr, Cu and Zn was found in the range of 0.04–3.42, 0.19–1.55, 0.27–2.45 and 0.32–1.57, respectively. Large variations in PI values of Pb revealed that soil in those areas of the city which are influenced by intensive anthropogenic activities have exceptionally high concentrations of Pb. The findings of this study would contribute to the environmental database of the soil of the region and would also facilitate both at the local and the international scales, in a more accurate global environmental monitoring, which will eventually facilitate the development of management and remediation strategies for heavy metal contaminated urban soil. 相似文献
5.
CDF it all: Consensus prediction of intrinsically disordered proteins based on various cumulative distribution functions 总被引:2,自引:0,他引:2
Many biologically active proteins are intrinsically disordered. A reasonable understanding of the disorder status of these proteins may be beneficial for better understanding of their structures and functions. The disorder contents of disordered proteins vary dramatically, with two extremes being fully ordered and fully disordered proteins. Often, it is necessary to perform a binary classification and classify a whole protein as ordered or disordered. Here, an improved error estimation technique was applied to develop the cumulative distribution function (CDF) algorithms for several established disorder predictors. A consensus binary predictor, based on the artificial neural networks, NN-CDF, was developed by using output of the individual CDFs. The consensus method outperforms the individual predictors by 4-5% in the averaged accuracy. 相似文献
6.
Yusuf Muhammad Noor Nurul Hidayah Samsulrizal Noor Azah Jema'on Kheng Oon Low Aizi Nor Mazila Ramli Noor Izawati Alias Siti Intan Rosdianah Damis Siti Fatimah Zaharah Mohd Fuzi Mohd Noor Mat Isa Abdul Munir Abdul Murad Mohd Firdaus Mohd Raih Farah Diba Abu Bakar Nazalan Najimudin Nor Muhammad Mahadi Rosli Md. Illias 《Gene》2014
Bacillus lehensis G1 is a Gram-positive, moderately alkalitolerant bacterium isolated from soil samples. B. lehensis produces cyclodextrin glucanotransferase (CGTase), an enzyme that has enabled the extensive use of cyclodextrin in foodstuffs, chemicals, and pharmaceuticals. The genome sequence of B. lehensis G1 consists of a single circular 3.99 Mb chromosome containing 4017 protein-coding sequences (CDSs), of which 2818 (70.15%) have assigned biological roles, 936 (23.30%) have conserved domains with unknown functions, and 263 (6.55%) have no match with any protein database. Bacillus clausii KSM-K16 was established as the closest relative to B. lehensis G1 based on gene content similarity and 16S rRNA phylogenetic analysis. A total of 2820 proteins from B. lehensis G1 were found to have orthologues in B. clausii, including sodium–proton antiporters, transport proteins, and proteins involved in ATP synthesis. A comparative analysis of these proteins and those in B. clausii and other alkaliphilic Bacillus species was carried out to investigate their contributions towards the alkalitolerance of the microorganism. The similarities and differences in alkalitolerance-related genes among alkalitolerant/alkaliphilic Bacillus species highlight the complex mechanism of pH homeostasis. The B. lehensis G1 genome was also mined for proteins and enzymes with potential viability for industrial and commercial purposes. 相似文献
7.
Podar D Scherer J Noordally Z Herzyk P Nies D Sanders D 《The Journal of biological chemistry》2012,287(5):3185-3196
Metal tolerance proteins (MTPs) are plant members of the cation diffusion facilitator (CDF) transporter family involved in cellular metal homeostasis. Members of the CDF family are ubiquitously found in all living entities and show principal selectivity for Zn(2+), Mn(2+), and Fe(2+). Little is known regarding metal selectivity determinants of CDFs. We identified a novel cereal member of CDFs in barley, termed HvMTP1, that localizes to the vacuolar membrane. Unlike its close relative AtMTP1, which is highly selective for Zn(2+), HvMTP1 exhibits selectivity for both Zn(2+) and Co(2+) as assessed by its ability to suppress yeast mutant phenotypes for both metals. Expression of HvMTP1/AtMTP1 chimeras in yeast revealed a five-residue sequence within the AtMTP1 N-segment of the His-rich intracytoplasmic loop that confines specificity to Zn(2+). Furthermore, mutants of AtMTP1 generated through random mutagenesis revealed residues embedded within transmembrane domain 3 that additionally specify the high degree of Zn(2+) selectivity. We propose that the His-rich loop, which might play a role as a zinc chaperone, determines the identity of the metal ions that are transported. The residues within transmembrane domain 3 can also influence metal selectivity, possibly through conformational changes induced at the cation transport site located within the membrane or at the cytoplasmic C-terminal domain. 相似文献
8.
Cupriavidus metallidurans CH34 has gained increasing interest as a model organism for heavy metal detoxification and for biotechnological purposes.
Resistance of this bacterium to transition metal cations is predominantly based on metal resistance determinants that contain
genes for RND (resistance, nodulation, and cell division protein family) proteins. These are part of transenvelope protein
complexes, which seem to detoxify the periplasm by export of toxic metal cations from the periplasm to the outside. Strain
CH34 contains 12 predicted RND proteins belonging to a protein family of heavy metal exporters. Together with many efflux
systems that detoxify the cytoplasm, regulators and possible metal-binding proteins, RND proteins mediate an efficient defense
against transition metal cations. To shed some light into the origin of genes encoding these proteins, the genomes of C. metallidurans CH34 and six related proteobacteria were investigated for occurrence of orthologous and paralogous proteins involved in metal
resistance. Strain CH34 was not much different from the other six bacteria when the total content of transport proteins was
compared but CH34 had significantly more putative transition metal transport systems than the other bacteria. The genes for
these systems are located on its chromosome 2 but especially on plasmids pMOL28 and pMOL30. Cobalt–nickel and chromate resistance
determinants located on plasmid pMOL28 evolved by gene duplication and horizontal gene transfer events, leading to a better
adaptation of strain CH34 to serpentine-like soils. The czc cobalt–zinc–cadmium resistance determinant, located on plasmid pMOL30 in addition copper, lead and mercury resistance determinants,
arose by duplication of a czcICAB core determinant on chromosome 2, plus addition of the czcN gene upstream and the genes czcD, czcRS, czcE
downstream of czcICBA. C. metallidurans apparently evolved metal resistance by horizontal acquisition and by duplication of genes for transition metal efflux, mostly
on the two plasmids, and decreased the number of uptake systems for those metals.
This paper is dedicated to Dr. Max Mergeay for a long time of cooperation, constructive competition and friendship. 相似文献
9.
Shingu Y Kudo T Ohsato S Kimura M Ono Y Yamaguchi I Hamamoto H 《Biochemical and biophysical research communications》2005,331(2):675-680
We have isolated a metal tolerance protein (MTP) gene, NgMTP1, from Nicotiana glauca (a potential phytoremediator plant) and two MTP genes, NtMTP1a and NtMTP1b, from Nicotiana tabacum. These three genes shared approximately 95% homology at the amino acid level. Heterologous expression of any of these three genes complemented Zn and Co tolerance in yeast mutants to a similar extent. In yeast, these proteins were shown to be located to vacuole membrane. These results suggest that the three MTPs operate by sequestering Zn and Co into vacuoles, thereby reducing the toxicity of these metals. 相似文献
10.