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281.
Rangasamy Anandham Pandiyan Indira Gandhi Soon Wo Kwon Tong Min Sa Yong Ki Kim Hyeong Jin Jee 《Archives of microbiology》2009,191(12):885-894
A thiosulfate-oxidizing facultative chemolithoautotrophic Burkholderia sp. strain ATSB13T was previously isolated from rhizosphere soil of tobacco plant. Strain ATSB13T was aerobic, Gram-staining-negative, rod shaped and motile by means of sub-terminal flagellum. Strain ATSB13T exhibited mixotrophic growth in a medium containing thiosulfate plus acetate. A phylogenetic study based on 16S rRNA gene sequence analysis indicated that strain ATSB13T was most closely related to Burkholderia kururiensis KP23T (98.7%), Burkholderia tuberum STM678T (96.5%) and Burkholderia phymatum STM815T (96.4%). Chemotaxonomic data [G+C 64.0 mol%, major fatty acids, C18:1 ω7c (28.22%), C16:1 ω7c/15 iso 2OH (15.15%), and C16:0 (14.91%) and Q-8 as predominant respiratory ubiquinone] supported the affiliation of the strain ATSB13T within the genus Burkholderia. Though the strain ATSB13T shared high 16S rRNA gene sequence similarity with the type strain of B. kururiensis but considerably distant from the latter in terms of several phenotypic and chemotaxonomic characteristics. DNA–DNA hybridization between strain ATSB13T and B. kururiensis KP23T was 100%, and hence, it is inferred that strain ATSB13T is a member of B. kururiensis. On the basis of data obtained from this study, we propose that B. kururiensis be subdivided into B. kururiensis subsp. kururiensis subsp. nov. (type strain KP23T = JCM 10599T = DSM 13646T) and B. kururiensis subsp. thiooxydans subsp. nov. (type strain ATSB13T = KACC 12758T). 相似文献
282.
Stringent mating-type-regulated auxotrophy increases the accuracy of systematic genetic interaction screens with Saccharomyces cerevisiae mutant arrays
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A genomic collection of haploid Saccharomyces cerevisiae deletion strains provides a unique resource for systematic analysis of gene interactions. Double-mutant haploid strains can be constructed by the synthetic genetic array (SGA) method, wherein a query mutation is introduced by mating to mutant arrays, selection of diploid double mutants, induction of meiosis, and selection of recombinant haploid double-mutant progeny. The mechanism of haploid selection is mating-type-regulated auxotrophy (MRA), by which prototrophy is restricted to a particular haploid genotype generated only as a result of meiosis. MRA escape leads to false-negative genetic interaction results because postmeiotic haploids that are supposed to be under negative selection instead proliferate and mate, forming diploids that are heterozygous at interacting loci, masking phenotypes that would be observed in a pure haploid double-mutant culture. This work identified factors that reduce MRA escape, including insertion of terminator and repressor sequences upstream of the MRA cassette, deletion of silent mating-type loci, and utilization of α-type instead of a-type MRA. Modifications engineered to reduce haploid MRA escape reduced false negative results in SGA-type analysis, resulting in >95% sensitivity for detecting gene–gene interactions. 相似文献
283.
A robust marker to describe mass, hydrophobicity and polarizability distribution holds the key to deciphering structural and folding constraints within proteins. Since each of these distributions is inhomogeneous in nature, the construct should be sensitive in describing the patterns therein. We show, for the first time, that the hydrophobicity and polarizability distributions in protein interior follow fractal scaling. It is found that (barring ‘all-α’) all the major structural classes of proteins have an amount of unused hydrophobicity left in them. This amount of untapped hydrophobicity is observed to be greater in thermophilic proteins, than that in their (structurally aligned) mesophilic counterparts. ‘All-β’(thermophilic, mesophilic alike) proteins are found to have maximum amount of unused hydrophobicity, while ‘all-α’ proteins have been found to have minimum polarizability. A non-trivial dependency is observed between dielectric constant and hydrophobicity distributions within (α+β) and ‘all-α’ proteins, whereas absolutely no dependency is found between them in the ‘all-β’ class. This study proves that proteins are not as optimally packed as they are supposed to be. It is also proved that origin of α-helices are possibly not hydrophobic but electrostatic; whereas β-sheets are predominantly hydrophobic in nature. Significance of this study lies in protein engineering studies; because it quantifies the extent of packing that ensures protein functionality. It shows that myths regarding protein interior organization might obfuscate our knowledge of actual reality. However, if the later is studied with a robust marker of strong mathematical basis, unknown correlations can still be unearthed; which help us to understand the nature of hydrophobicity, causality behind protein folding, and the importance of anisotropic electrostatics in stabilizing a highly complex structure named ‘proteins’. 相似文献
284.
285.
Our understanding of ion permeation through K(+) channels, and by extension through other channels, is advancing rapidly. New structural studies, together with computer simulations, have provided profound insights into ion conduction mechanisms. 相似文献
286.
The structural properties of melittin, a small amphipathic peptide found in the bee venom, are investigated in three different
environments by molecular dynamics simulation. Long simulations have been performed for monomeric melittin solvated in water,
in methanol, and shorter ones for melittin inserted in a dimyristoylphosphatidylcholine bilayer. The resulting trajectories
were analysed in terms of structural properties of the peptide and compared to the available NMR data. While in water and
methanol solution melittin is observed to partly unfold, the peptide retains its structure when embedded in a lipid bilayer.
The latter simulation shows good agreement with the experimentally derived 3J-coupling constants. Generally, it appears that higher the stability of the helical conformation of melittin, lower is the
dielectric permittivity of the environment. In addition, peptide-lipid interactions were investigated showing that the C-terminus
of the peptide provides an anchor to the lipid bilayer by forming hydrogen bonds with the lipid head groups. 相似文献
287.
P K Mohan L V Reddy N Satyanarayana K Indira 《Archives internationales de physiologie et de biochimie》1987,95(1):37-42
The changes in the pattern of production and detoxification of ammonia have been studied in the skeletal muscles and blood of rats of different age groups (1, 3, 6, 12 and 24 months), subjected to exhaustive exercise. The protein profiles at exhaustion showed a sharp drop in all muscles and the decrement was more in the senile rats. In general, the muscle and blood ammonia content increased with age with a corresponding increase in AMP deaminase activity implicating the possibility of elevated purine nucleotide deamination during senescence. However, glutamate oxidation was decreased and urea and glutamine formation was increased consequent to ammonia production during senescence under intensive physical stress. The possible alterations in protein levels and ammonia production and its disposal in different skeletal muscle types of senile exhausted rats have been discussed in relation to detoxication capacity of the fibre types. 相似文献
288.
289.
290.
K Satyavelu Reddy V Mohanachari K Indira 《Archives internationales de physiologie et de biochimie》1982,90(4):285-291
Lactate (LDH) and succinate (SDH) dehydrogenases activities decreased in red and white muscles of rat under acute ethanol loading indicating the inhibition of energy metabolism and stepped up lactic acid formation under stress conditions. Aspartate aminotransferase (AAT) and glutamate dehydrogenase (GDH) were found to increase. In contrast to these, the AMP deaminase activity decreased in white muscle suggestive of decreased deamination of nucleic acids. The ornithine cycle enzymes such as argininosuccinate synthetase (ArSS) and arginase indicated diminished activities showing low level of operation of urea cycle and consequent accumulation of ammonia was observed in red muscle with low production of glutamine, whereas in the case of white muscle this trend is reversed. The possible alterations of ethanol toxicity on energy requirements, transdeamination patterns, ureogenesis and glutamine production have been discussed. 相似文献